The questionnaire used in the study consisted of both open and closed questions and addressed the following areas: drug use before and during imprisonment (including the drugs used, the method of drug administration, and the frequency of drug use), the response of the prison to drug use, and the effect and potential of the prison environment on drug use. Inmates at the sampled prison were all Category B prisoners; it is not apparent that the drug use of such a population would be representative of the prison population as a whole. A total of 140 questionnaires were randomly distributed among the general prison population; 61 percent (n=85) were returned. Of the respondents, 28.4 percent had been charged and sentenced under the Misuse of Drugs Act. A further 32.4 percent reported that their offense was drug- related. The results suggest that for the majority of individuals, drug use will decrease during imprisonment. There was no decrease in the range of drugs used, but the availability and popularity of the range used by the respondent did differ between the community and prison; however, nearly half of those respondents who claimed not to be using drugs before imprisonment started using drugs once imprisoned. The inmates perceived that the prison environment was not supportive for those who wished to abstain from drug use. Although the results suggest that for the majority of inmates drug use will decrease during imprisonment, most probably due to reduced availability, the prison environment does not support those individuals who wish to stop their drug use. Any positive impact of the environment on the individuals is outweighed by the negative impact it presented for the majority of respondents. For most respondents, the prison environment encouraged drug use. 10 tables, 3 notes, and 19 references