Between April and June 1993, 8 cases of acute clinical hepatitis B infection and 2 seroconversions to HIV infection were detected among drug injecting inmates of HM Prison Glenochil in Scotland. To prevent the further spread of infection, an initiative which involved counselling and voluntary attributable HIV testing was conducted over a 10-day period commencing at the end of June. A team of 18 counsellors and phlebotomists was brought together rapidly as part of a unique organizational exercise in the field of public health. Fourteen cases of HIV infection were identified of which 13 were almost certainly infected in Glenochil. Following the exercise, a range of harm reduction measures for injecting prisoners was introduced; these included the availability of hepatitis B vaccine, provision of bleach tablets which could be used to clean injecting equipment, a methadone detoxification programme, increased training for prison officers and improved access to drug and harm minimization counselling for inmates. By mid-1996 all these measures had been sustained and several could be found in many other prisons throughout Scotland. Follow-up investigations showed no evidence of epidemic spread of HIV during the 12 months after the initiative. While the frequency of injecting and needle/syringe sharing may have decreased over the last 3 years, these activities are still being reported and it is highly likely that transmissions of bloodborne infections, in particular hepatitis C, continue to occur. The surveillance and prevention of infections associated with injecting drug use in the prison setting remain a high public health priority.