He became professional in 1973. The highlight of his career was his overall win in the 1977 Giro d’Italia.

In the 1978 Tour de France, he was the Belgian national champion when he won the stage arriving in Alpe d’Huez and took the yellow jersey. However, he was accused of foul play in the succeeding doping test, having used what was described politely as a pear-shaped tube (in fact, a condom) of different urine held under the armpit and connected by a plastic tube to give the impression of urinating. Pollentier was uncovered after another rider at the test had trouble operating his own system of tubes and aroused the suspicion of the doctor, who then demanded Pollentier lift his jersey to show if he too was cheating. He was put out of the Tour, later won by Bernard Hinault.

The affair took away most of Pollentier’s credibility in international cycling. Even though he won the 1980s edition of the Tour of Flanders, he also came 2nd in 1982 Vuelta a España. 1984 was his last professional season. After his cycling career, Pollentier became a car tire garage owner and founded a cycling school.

In “Seigneurs et Forcats du Velo” by Olivier Dazat, Pollentier is quoted as saying that he and another named Belgian cycling champion of the era had trouble after their careers because of drugs they had taken while racing. Dazat quotes him as saying: “I’ve never hesitated to confess that I spent three weeks under the surveillance of Dr. Dejonckheere at the St-Joseph clinic at Ostend and that after treatment… I stayed under his control for another two years. Why hide it? It’s impossible to come out of a situation like that without the help of a doctor.’