In order to assess patterns of antibiotic prescribing and self-medication, a survey was carried out of patients from Government and private hospitals (500 each) and of 1000 apparently healthy adults in Benin City, Nigeria. Ampicillin and tetracycline were the antibiotics commonly used for self-medication; the commonest reasons given for the self-medication were the treatment of sexually transmitted diseases, cough, stomach upsets and diarrhoea. Ampicillin was the commonest prescribed antibiotic; the commonest indications for prescription were soft-tissue, sexually transmitted, upper respiratory and gastro-intestinal infections. According to an assessment by four clinicians from a panel of eight in Government and private practice, 52% of the total prescriptions were judged to be appropriate whereas 30% were judged to be inappropriate by a majority of the physicians. The implications of this study for the control of bacterial resistance to antibiotics are discussed.