Compliance with prescribed drug treatment within two weeks of discharge from hospital was studied in 50 patients discharged from acute medical wards. Patient knowledge about medicines and factors influencing compliance were investigated. A combination of tablet counts and questionnaires was used. Eleven patients were found to have deviated from the prescribed regimen. The prescribing of complex drug regimens appeared to be one of the factors affecting non-compliance. Patient knowledge about their medicines was generally poor, with less than one quarter knowing the names and purposes of all their medicines, and 70 per cent not knowing about any single side effect their medicines could cause. No correlation was found between poor knowledge and non-compliance. The attitudinal questionnaire used was not helpful in identifying non-compliers.