1987: two-year-old season

On her racecourse debut, Dark Lomond contested a maiden race over six furlongs at the Curragh in October and finished strongly to take second place, three quarters of a length behind the John Oxx-trained Catina. At the end of the year the independent Timeform organisation gave her a rating of 88 p (the "p" indicating that she was expected to make more than usual improvement) and commented in their annual Racehorses of 1987 that she was "sure to win races".^[5]

1988: three-year-old season

Dark Lomond was ridden by John Reid in her first four races as a three-year-old. On her seasonal debut she started the 4/6 favourite for a Listed race over ten furlongs on heavy ground at Phoenix Park Racecourse on 4 May but was beaten into second place by the outsider Viqueen. The ground was much lest testing when she returned to Phoenix Park in June for the Phoenix Oaks Trial over eleven furlongs. She was made the 7/4 favourite and won by four lengths from Host of Angels, with Viqueen trailing in last of the ten runners.^[6] Later that month the filly was stepped up in class for the Group 2 Pretty Polly Stakes at the Curragh and started 15/8 favourite ahead of her stablemate Dancing Goddess, who had finished second in the Irish 1000 Guineas on her last start. After being restrained by Reid in the early stages, she moved into contention in the last quarter mile and then produced a strong late run up the inside rail to win by a length and a neck from Skating and Ardglen.^[7]

After a break of over two months Dark Lomond returned in the Meld Stakes at the Curragh on 27 August, and finished second, half a length behind the British-trained filly Sailors Mate, to whom she was conceding five pounds in weight. Declan Gillespie took over from Reid when Dark Lomond was the only three-year-old filly in the thirteen-runner field which contested the Irish St Leger over fourteen furlongs at the Curragh on 24 September. The 1987 winner Eurobird started favourite ahead of Zaffaran (March Stakes), Heavenly Manna (Royal Whip Stakes) and Kris Kringle (Derrinstown Stud Derby Trial) with Dark Lomond next in the betting on 10/1. Dark Lomond was towards the rear of the field before moving up into sixth place behind Waterfield on the final turn. Kris Kringle went to the front but Dark Lomond overtook him a furlong and a half from the finish and stayed on well to win by three lengths from Daarkom. Eurobird took third place ahead of Alwasmi with Kris Kringle fading into fifth.^[8]

On her penultimate appearance Dark Lomond contested Europe's most prestigious weight-for-age race, the Prix de l'Arc de Triomphe over 2400 metres at Longchamp Racecourse on 2 October. She never looked likely to win but stayed on in the straight to finish eleventh of the 24 runners, seven and a half lengths behind the winner Tony Bin. She returned to Longchamp three weeks later for the Prix Royal Oak over 3100 metres. After racing at the rear of the sixteen-runner field he made some progress in the closing stages and finished sixth behind the four-year-old colt Star Lift.