Hislop grew up in the village of Chesters near Hawick in the Scottish Borders, encouraged from an early age by his father Sandy to take up competitive motorcycling. Tragedy struck in 1982 when his younger brother Garry — his closest friend — was killed in a racing accident at Silloth circuit at age 19. Hislop fell into a period of depression and alcohol, compounded by the earlier loss of his father to a heart attack. He eventually returned to racing and transformed personal grief into some of the most memorable performances in road racing history.
Hislop made his Isle of Man debut in 1983 at the Manx Grand Prix, finishing second in the newcomers' race. Over the following years he built an outstanding TT record, accumulating eleven victories across multiple classes.
His most celebrated TT performance came in the 1992 Senior TT, frequently cited as one of the greatest races in the event's history. Hislop rode a Norton 588 prepared by Ron Haslam's team, distinguished by its unconventional white livery sponsored by Abus. The Norton had been modified specifically for the Senior race — a larger screen was added to protect Hislop from high winds, the front mudguard was removed to improve engine cooling, and protective fork covers were fitted.
His chief rival was Carl Fogarty, starting at number four compared to Hislop's number nineteen. The staggered start meant Hislop had more traffic to navigate, yet the time gap between the two riders never exceeded 7.4 seconds across the entire race. The pair repeatedly shattered records they had set the year before. On the final lap, Fogarty recorded a lap exceeding 123 mph on his Yamaha in a last attempt to close the gap, but Hislop guided the Norton home first — a result made all the more remarkable given that the Norton was competing against purpose-built Grand Prix machines from major manufacturers.
Away from the island roads, Hislop proved equally formidable on short circuits. His first national championship came in 1990, winning the British 250cc title. He then won the British Superbike Championship in 1995. In 1998 he joined Rob McElnea's Cadbury's Boost Yamaha team, where a fierce championship battle with teammate Niall Mackenzie produced one of the most intense BSB title fights of the decade. A near-collision between the two on the final lap at Snetterton underscored the intensity of the duel, though an injurious crash ultimately removed Hislop from title contention that year.
His final championship triumph came in 2002 on a Ducati, taking his second BSB title. That season he notably lapped Donington Park on his production-derived Ducati faster than the fastest MotoGP machine at the same circuit — a remarkable achievement given the superbike was both heavier and less powerful than the bespoke Grand Prix machinery.
On 30 July 2003, Hislop died when the Robinson R44 helicopter he was piloting crashed near Teviothead in Roxburghshire. He was buried in the village of Chesters, close to where he grew up.
Knickerbrook Chicane at Oulton Park was renamed Hislops Chicane in his memory following circuit redevelopment over the 2003–04 winter. A bronze statue stands on Onchan Head on the Isle of Man, and a ground-level life-sized bronze statue in his racing leathers was erected in Wilton Park in Hawick. A museum room dedicated to Hislop at Wilton Park displays trophies, motorcycles, and personal effects. The annual Hizzy Run, originating from Denholm Green, was established in 2003 by friend and fellow racer Alan Duffus to fund the memorial statues; the event continues to draw hundreds of riders each year. In March 2010, Hislop was posthumously inducted into the Scottish Sports Hall of Fame.