Gert -Jan Theunisse ( born January 14, 1963 in Oss, Netherlands ) is a former Dutch cyclist.
He was in the years 1984 to 1995 pro, winning 15 races at this time.
Five times he contested the Tour de France. In his second appearance in 1988 he tested positive during a doping control on testosterone and assigned a 10 minute time penalty, so that he fell back from fourth to eleventh place in the overall standings. After the Tour de France he won this year, the Clasica San Sebastian.
In 1989 he achieved fourth place its best overall ranking and won the mountain stage to L' Alpe d' Huez and the polka-dot jersey of the winner of the mountains classification.
In 1990, he was tested at the Flèche Wallonne and Bicicleta Vasca the two other times positive in doping controls.
In 1995, he finished his career after he got heart problems in Tirreno- Adriatico. After his career end Theunisse was like other Dutch professional cyclists to years of doping. Whether his heart problems are related to the doping use is unclear.
In December 2013 Theunisse reported in a column of the journal Wielerrevue after a heart attack, a pacemaker to have to get used. He had previously suffered dozens unnoticed infarcts.
- Clasica San Sebastian
- A stage and Tour de France Polka Dot jersey
- Asturias Tour