Stage 17, which finished at Alpe d'Huez, one of the most famous climbs in cycling, was expected to be the decisive part of the race overall. Theunisse, wearing the polka-dot jersey as leader of the mountains classification, attacked on the first climb, the Col du Galibier. He was joined by two more riders, Franco Vona (Chateau d'Ax) and Laurent Biondi (Fagor-MBK) before the ascent of the Col de la Croix de Fer, but rode away from his breakaway companions before he reached the summit. At Le Bourg-d'Oisans, the village before the climb to Alpe d'Huez starts, he led the group of favourites by more than four minutes and held on to win the stage by over a minute. Behind him, the battle for the yellow jersey intensified. Fignon, LeMond and Delgado entered the climb together and Fignon instantly attacked at the first hairpin bend. LeMond stuck to his wheel, but Guimard, knowing LeMond well from their days together at the Renault team, saw that he was struggling. He drew his team car level with Fignon and ordered him to attack again with to go to the finish line. LeMond fell back and only Delgado was able to keep up with Fignon. The two reached the finish together, 1:19 minutes ahead of LeMond. Fignon thus regained the yellow jersey, with an advantage of 26 seconds over LeMond.