Drug interactions are a common cause of iatrogenic disease in geriatric patients. Computer programs now exist which allow one to analyse groups of drugs for potential interactions. In an audit of charts of 100 geriatric patients seen in the Family Practice Center at Barberton Citizens Hospital, a computer print out was obtained, listing all patients aged 60 years and over who were seen at the Center during 1989. Names were selected randomly from this list by the head nurse and their charts were obtained for review, generating information on patient identification number, age, sex, diagnoses, medications, and allergies. The medications were analysed using the Hansten Drug Interaction Knowledge Base Program, which identified 27 patients as being on a combination of medications which had one or more potential drug interactions. A total of 37 potential drug interactions were identified in this group of 27 patients. Relative risk ratios were determined using the computer program, ‘Epi Info,’ for sex (female versus male), age (≥75 vs. 60–75 years), number of diagnoses ≥3 vs. 0–2), and number of medications (≥4 vs. 0–3). The five medications, or groups of medications, which were most likely to be involved in potential drug interactions were digoxin, β-blockers, oestrogen, oral hypoglycaemic agents, and diuretics.