Maria McMahon:Tested positive at the 1996 Olympics in Atlanta. The 5,000-metre runner took an over-the-counter cold remedy containing the banned substance Phenylpropenoamine and received a warning.
Geraldine Hendricken:Tested positive for the prohibited steroid nandrolone in the 2003 season. The international 1,500-metre runner received a two-year ban.
Gareth Turnbull:The Belfast distance runner was found to have elevated levels of testosterone in his system in 2004 and banned for two years. He fought the case in the courts, reputedly spending €100,000, before being exonerated.
Cathal Lombard:The 10,000-metre runner tested positive in 2004 for EPO, a protein hormone that stimulates the production of red blood cells. He acknowledged that he had cheated and was banned for two years.
Michelle De Bruin:Won three gold medals and a bronze medal in Atlanta in 1996. In 1998, the swimmer was banned for four years for tampering with a sample, when what would have been lethal amounts of alcohol if consumed, were found in her urine sample.
Cian O'Connor:The showjumper won the individual gold medal in Athens in 2004 but was forced to hand it back when a sedative was found in the system of his horse, Waterford Crystal. He received a three-month ban.
Jessica Kürten:Her horse, Castle Forbes Maike, tested positive in 2007 for etoricoxib, a non-steroidal anti-inflammatory drug. She was suspended but challenged the decision in the Court of Arbitration for Sport (CSA). CSA stayed the suspension until a hearing takes place, probably next month.
Andrew Bree:The Irish record holder in the 200-metre breaststroke tested positive earlier this year for methamphetamine after taking a Vicks inhaler in America. He was warned but not prevented from competing in Beijing.