Five players at Aviva Premiership clubs tested positive for recreational drugs in the 2012-13 season, the Rugby Football Union has announced.
The RFU's third anti-doping annual report reveals that 345 tests took place as part of the illicit drugs programme, which conducts out of competition tests for common illicit drugs.
Five positive results were returned, but these cases are treated confidentially as they are first offences, resulting in a 'first strike' fine of £5,000 and access to assessment, rehabilitation and counseling.
It is the first time since the illicit drugs programme was introduced for the 2009-10 season that there have been violations of the policy.
Four major illicit drug groups are tested - cocaine, cannabis, ecstasy and amphetamines - and 83 per cent of samples are hair samples, which have a three to seven month detection period.
"A small number of adverse findings via the illicit drugs programme is a reminder that we can never assume the anti-doping job has been 'done'," Rugby Players' Association rugby director David Barnes said.
There were a total of 617 in and out of competition tests for performance-enhancing drugs.
All five of the positive tests for the 2012-13 season were recorded at National League level and below. A Premiership player has yet to return a positive test for performance-enhancing drugs.
"It is reassuring to see another season concluded with no systemic doping amongst the senior elite players in England. They continue to be role models for the wider game," Barnes said.