On May 4, 1968, Dancer's Image had a thrilling win at the Kentucky Derby, surging from last to first across the finish line. Soon afterward, the stallion tested positive for phenylbutazone, an anti-inflammatory. The drug was not allowed to be present on race day at the Derby, though use was permitted at other times for pain-alleviation, so Dancer's Image's win was erased. Owner Peter Fuller contested the disqualification in court for years, spending more than the $122,000 prize money, but was ultimately unsuccessful.

Fuller was left with a theory about what had happened. A supporter of civil rights, he'd given $60,000 in winnings from another race to Coretta Scott King in the wake of Martin Luther King Jr.'s assassination. This became public knowledge, resulting in threats, but Fuller's request for enhanced security before the race had been turned down. Someone could have approached Dancer's Image and drugged him.

In the early 1970s, Anthony Ciulla, known as "Big Tony," bribed jockeys in hundreds of races. They would usually be told to slow their horses so they didn't finish in the top three, thus ensuring that less favored horses won and delivered big payouts. Ciulla once declared he'd been a fixer in all states with horse racing except California.

In a race at Atlantic City in 1975, the jockey Ciulla had influenced was too obvious about reining in his horse. When asked why, he revealed Ciulla's involvement. While Ciulla was behind bars, the FBI offered a deal: His sentence would be shortened if he helped with an ongoing federal investigation into horse racing. Ciulla ended up testifying against the jockeys and trainers who'd fixed races for him before being granted entry into the Witness Protection Program.

In 1974, Tony Murphy, an Irish millionaire with a passion for horse racing, attempted to pull off a horse racing bait and switch. He arranged for an unknown horse, who he referred to as winning horse Gay Future, to be trained by Antony Collins in the United Kingdom. In reality, the horse was actually a similar-looking imposter to the real Gay Future. Because the horse didn't appear promising and it decreased the odds of him winning an upcoming August 26 race in Cartmel. However, before the race, the real Gay Future was brought to England from Ireland to be swapped in secret. And in an attempt not to alert bookmakers, Murphy entered two other Collins-trained horses, though he never planned on actually having them race.

On race day, conveniently the same day as nine other larger races, the two other horses were officially pulled from competition, leaving Gay Future and one other horse left. To deter those at the racecourse from betting on Gay Future and therefore increasing his winning odds, his legs were covered with soap to make him appear sweaty. Of course, Gay Future won. However, the scheme fell apart when a reporter learned that the other horses hadn't even traveled to their racecourses. Murphy and Collins were convicted of attempted fraud but did not go to prison.

Dr. Mark Gerard, a veterinarian who'd taken care of Secretariat when that horse won the Triple Crown in 1973, served as the agent to import two horses—Cinzano and Lebon—from Uruguay to the United States in June 1977. Cinzano had been Uruguay's Horse of the Year in 1976, while Lebon was nowhere near that level. After the horses' arrival at Gerard's farm, Cinzano's accidental death was recorded.

At New York's Belmont Park on September 23, 1977, Lebon defied the odds to win his race, earning Gerard $80,000. But soon an Uruguayan journalist notified the New York Jockey Club that the winning Lebon was actually Cinzano—the two horses looked similar, but the white stars on their foreheads were different. Their identities had been switched, and Gerard served time behind bars for the scheme.

Shergar was a famous racehorse who won the Epsom Derby by the largest margin in race history. He won other races, including the Irish Derby, before his retirement in 1981 to work as a stud in Ireland. On February 8, 1983, masked gunmen came to Shergar's farm, forced a groom to load up the horse, and drove away. It took time for the police to be contacted, lowering the chances of tracing Shergar.

A $3 million demand for ransom came, but Shergar's owners—the Aga Khan and other shareholders—decided not to pay, leery of future abductions. There have been suggestions the crime was committed by the mafia or Libya's Muammar Gaddafi, but the most accepted theory is that the stallion was taken and killed by the IRA in a botched attempt to fund the group. Shergar's remains have never been discovered.

Fine Cotton was not a successful Australian racehorse when he was purchased by bloodstock agent John Gillespie. Gillespie also acquired Dashing Solitaire, a better racer who resembled Fine Cotton. The plan was simple: run Dashing Solitaire in Fine Cotton's place at a race on August 18, 1984. The scheme went off the rails when Dashing Solitaire was injured in a kangaroo-related incident and left unable to run.

Instead of giving up, Gillespie and conspirators decided to run another horse, Bold Personality, whose color and markings were nothing like Dashing Solitaire and Fine Cotton. To address this, Gillespie's gang used hair dye, which turned the horse orange. The dye was rinsed off, then spray paint was applied to mimic Fine Cotton's white socks. The horse ran, and won—but the subterfuge was quickly discovered, in part because paint was dripping down the horse's legs. Gillespie and his trainer ended up serving time.

After the Breeders' Cup race on October 26, 2002, Derrick Davis had winning Pick Six tickets—in which bettors try to select the winners in six consecutive races—and won more than $3 million. Yet the circumstances of his success seemed suspicious: Davis was the only person with winning Pick Six tickets, had selected two long-shot winners and had made the unusual choice to pick winners in the first four races while selecting all horses to win in the last two races.

An investigation discovered that Chris Harn, one of Davis' fraternity brothers, was a senior computer programmer at Autotote, which handled the telephone betting service that Davis used. Harn had been able to make changes in Autotote's system after the first four races had been run, which let him select the winners for Davis' tickets. Harn had also rigged bets with another fraternity brother, Glen DaSilva. DaSilva, Davis and Harn all received prison sentences ranging from one year to 37 months.

During California racetrack Santa Anita Park's December 2018 to June 2019 season, 30 horses died, with 23 of these deaths occurring by the end of March. The losses resulted in public outcry, increased attention on the conditions and treatment of racehorses and official inquiries. The track temporarily shut down, then decided to phase in a ban of Lasix, which is used to prevent bleeding in horses' lungs. As a diuretic, it also makes horses lose weight before a race.

There was speculation that the dirt track's conditions, perhaps affected by heavy rains, had caused the deaths, but tests showed nothing was amiss. Though the California Horse Racing Board's inquiry discovered problems, such as trainers feeling pressured to have horses run and poor record-keeping, illegal drugs and procedures were not found responsible for the deaths.

In March 2020, U.S. federal prosecutors indicted 27 trainers, veterinarians and drug distributors. The charges alleged the use of "drugs designed to secretly and dangerously enhance the racing performance of horses beyond their natural ability, a dishonest practice that places the lives of affected animals at risk." Some of the drugs used were referred to as "red acid," "bleeder" and "frozen pain." A veterinarian was accused of distributing cobra venom as a painkiller.

Among the indictees were top-level trainers. These included Jason Servis, who trained Maximum Security. Maximum Security had crossed the finish line first at the Kentucky Derby in 2019, but was disqualified for interference, and had won $10 million in the Saudi Cup on February 29, 2020. Jorge Navarro, trainer for XY Jet, was also indicted. XY Jet received $1.5 million at the Dubai Golden Shaheen in 2019 but supposedly died from a heart attack in January 2020.

On May 1, 2021, Medina Spirit won the Kentucky Derby. He then made headlines for failing a drug test after the race; the level of betamethasone, an anti-inflammatory, in his system violated Kentucky's medication protocols. The failed test also brought negative attention to Medina Spirit's trainer, Bob Baffert. Baffert's horses have failed 30 drug tests over 40 years, with Medina Spirit becoming the fifth horse to do so in the past year.

The situation highlights the importance of the Horseracing Integrity and Safety Act, which will institute national standards for drugs and medication, along with testing and enforcement measures, when it takes effect on July 1, 2022.