1982: two-year-old season

Tolomeo ran three times as a two-year-old in 1982, finishing second in his first two attempts before recording his first win in a maiden race over seven furlongs at Newmarket Racecourse.^[2]

1983: three-year-old season

After finishing fourth in the Craven Stakes on his debut as a three-year-old, Tolomeo contested the classic 2000 Guineas over Newmarket's Rowley mile course on 30 April. Ridden by the Italian jockey Gianfranco Dettori he started at odds of 18/1 against fifteen opponents. He was restrained in last place for most of the way before making rapid progress in the last quarter mile to finish second to the Irish-trained Lomond. Dettori was criticised for giving the colt too much ground to make up, but Cumani defended his jockey, insisting that he was riding according to instructions. Tolomeo next ran in The Derby over one and a half miles on soft ground, finishing ninth of the twenty-one runners, more than twenty lengths behind the winner Teenoso. Following the Derby, Tolomeo returned to shorter distances and produced three good performances without winning. He finished second by a head to Horage in the St James's Palace Stakes, third in a blanket finish for the Eclipse Stakes and second to the five-year-old Noalcoholic in the Sussex Stakes.^[2]

In August, Tolomeo was one of four British-trained horses sent to Chicago for the third running of the Budweiser Million, which was then the most valuable horse race in the world.^[3] British horses had performed well in the first two runnings of the race: Madam Gay had finished third in the inaugural running, and a year later Be My Native and Motovato had finished second and third behind Perrault. The "home team" was headed by the eight-year-old John Henry, supported by Majesty's Prince, Nijinsky's Secret and Erins Isle. Tolomeo was ridden by the Irish jockey Pat Eddery and started at odds of 38/1 in a fourteen-runner field, although British bookmakers were much more cautious and made the colt the 5/1 second favourite.^[1] In a slowly run race, Eddery tracked the leaders John Henry and Nijinsky's Secret before making his challenge in the straight. When Nijinsky's Secret drifted to the right under pressure Tolomeo accelerated through a gap along the rail to take the lead and held of the late run of John Henry to win by a neck.^[3] Tolomeo's success was the first for a British-trained horse in a major American race since Karabas won the Washington, D.C. International in 1969. His win also made him the second biggest money-earner in British racing history behind the 1979 Derby winner Troy.^[2]

On his return to Europe, Tolomeo ended his season with a run in the Champion Stakes at Newmarket in October. In a race which was run in a very strong side-wind, he finished second to the filly Cormorant Wood, but was relegated to fourth for causing interference in the closing stages.^[2]

1984: four-year-old season

As a four-year-old, Tolomeo continued to produce good performances but was less consistent and Timeform commented that he appeared to have become "something of a character". On his first appearance of the year he finished fourth when carrying top weight in the Prince of Wales's Stakes (then a Group Two race) and then finished seventh behind Sadler's Wells in the Eclipse Stakes. In July he was moved up in distance to one and a half miles for the King George VI and Queen Elizabeth Stakes at Ascot. Ridden by his regular work-rider Rae Guest, Tolomeo produced one of his best efforts as he finished third behind Teenoso and Sadler's Wells. In August he finished second in the Benson and Hedges Gold Cup at York, beaten two and a half lengths by Cormorant Wood. His form declined in the autumn and he finished unplaced in the Phoenix Champion Stakes and the Champion Stakes.^[4]