1985: three-year-old season

After finishing third over 2000 metres on his racecourse debut, Saint Estephe recorded his first win in a race over 2100 metres at Saint-Cloud Racecourse in April. He was then moved up in class and finished third behind Mouktar in the Prix Hocquart at Longchamp in May and second to Iades in the Prix du Lys at Chantilly in June. In July the colt was matched against older horses in the Prix Maurice de Nieuil at Saint-Cloud. Ridden by Alfred Gibert he won by half a length from the four-year-old Complice with the German challenger Abary in third place. In the Prix Niel at Longchamp in September he finished second by a nose to Mouktar in a photo finish. On his final appearance of the season Saint Estephe was ridden by Lester Piggott and started odd-on favourite for the Prix du Conseil de Paris and finished third behind Jupiter Island and Baby Turk.^[2]

1986: four-year-old season

On his first appearance as a four-year-old Saint Estephe contested the Group Three Prix d'Harcourt over 2000 metres at Longchamp in April and won by six lengths from Over the Ocean, the winner of the European Free Handicap and Prix Perth. In the Prix Ganay on 4 May he started odds-on favourite but was beaten a short head and half a length into third place behind Baillamont and Mersey with Triptych in fourth. On 5 June Saint Estephe and Triptych represent France in the 81st running of the Coronation Cup over one and a half miles at Epsom Racecourse. Shardari started favourite ahead of Petoski and Phardante (a winner over Slip Anchor in the Jockey Club Stakes) with Saint Estephe, ridden by Pat Eddery, starting a 20/1 outsider in a ten-runner field. After being restrained at the rear of the field he moved up on the outside to track the leaders early in the straight and gained the advantage from Triptych inside the final furlong. Saint Estephe hung to the left in the closing stages, but held off the renewed challenge of Triptych to win by a short head.^[3]

Saint Estephe attempted to add a second Group One victory a month later in the Grand Prix de Saint-Cloud but was beaten two lengths into second place by the German colt Acatenango. After a summer break he returned in September for the Prix du Prince d'Orange, a trial race for the Prix de l'Arc de Triomphe, and finished second to the filly Fitnah (Prix Saint-Alary) with the hitherto undefeated Fast Topaze (Poule d'Essai des Poulains) in third. In an exceptionally strong renewal^[6] of the Prix de l'Arc de Triomphe on 5 October Saint Estephe finished ninth of the fifteen runners behind Dancing Brave, beaten seven and half lengths by the winner. He sustained a leg injury during the race and finished lame.^[3]