 Demeyer was one of the so-called "Three Musketeers", riding with and for Freddy Maertens and Michel Pollentier He led out sprints for Maertens in particular but could win them for himself, including stages of the Tour de France.He rode the Tour six times, finishing 72nd in 1973, 41st in 1974, 42nd in 1975, 56th in 1976, 49th in 1978 and 57th in 1979.He won the intermediate sprints competition, known then as Points Chaud ('hot spot sprints') in the Tours of 1973 and 1975.