Inmates at an open prison are reportedly getting Viagra for day trips out on licence.
The blue pills are being smuggled in to prisoners who are allowed out of jail as part of their rehabilitation.
Officials said stashes of the pills were reported at Springhill prison in Grendon Underwood, Buckinghamshire.
The category D jail is home to 255 inmates some of whom are released on temporary licence - ROTL - to work or visit family as part of their rehabilitation.
But crafty lags planning nookie during their release have been ordering Viagra, which cures impotence, from prison drug dealers.
A prison source said: "All kinds of drugs are available in the jail from Ecstasy to cocaine and cannabis but Viagra is the most popular because of the men allowed out on temporary licence.
"There is a steady trade in it and lads who know they are getting out for a day or two will pay top price.
"They are meant to be working or visiting children or sick relatives but a lot of them have obviously got other ideas."
Prison inspectors found evidence Viagra as well as the use of prescription tranquillisers pregabalin, gabapentin as well as the mind-bending hallucinogenic drug Spice.
The report by the Independent Monitoring Board said: "Cannabis continued to be prevalent on camp.
"Fifty per cent of finds related to cannabis, but during the year there were also significant finds of pregabalin and gabapentin, as well as intelligence on Spice, opiates, steroids, Viagra and cocaine."
The report said it was likely that men released on temporary licence smuggled the Viagra back into the prison on their return and sold it to other inmates.
It added: "Reports of intruders on the camp were significantly reduced and finds suggest that drugs and contraband were more likely to have been brought in through other ways, such as ROTL."
Inmates at the open prison are considered trustworthy and include those coming to the end of long sentences or those serving short sentences.
Prisoners are addressed as "residents" and live in thirteen huts, many two to a room, and huts have a communal lounge, kitchen, showers and separate toilets.
