This paper reports on a survey of all medicines dispensed within the prison service which was carried out on November 29th 1984. Particular attention was given to sleeping tablets (hypnotics) and mood-changing drugs (anti-depressants and tranquilizers) i.e. psychotropics. Of 1599 inmates 337 received one or more prescribed medicines, 206 or 61% received a psychotropic drug. One half of juveniles receiving medicine received a psychotropic drug compared with 62% of adult males and 63% of females. There is a large variation between centres in medication rates, ranging from 0% in Shanganagh Castle to 58% in Mountjoy Female. It is important to note that these statistics refer to a single day and that psychotropic medicine is in almost all cases prescribed for far longer periods of time than non-psychotropic medicine. Several inmates were receiving a tranquilizer, hypnotic or anti-depressant for periods in excess of one year.