Drug prescribing patterns were studied retrospectively in 600 patients admitted to the medical wards of three Government hospitals and one private nursing home in the Kandy area of Sri Lanka. The mean drug exposure in the governmental institutions varied between 3.6 and 3.7, whereas at the private institution, patients were exposed to an average of 7.2 drugs. The three Government institutions used 87, 91 and 107 drugs. The private institution 201. There was no difference in drug exposure in relation to sex, but a tendency towards increased drug exposure was noted with increasing age and longer duration of stay. Antimicrobial agents were the most frequently prescribed class of drugs and diazepam the most prescribed single drug. The reasons for the extensive use of diazepam observed in this study are not clear.