Patient compliance with prescriber's medication instructions was investigated in 178 rheumatoid arthritis patients treated in community practice. The compliance rate in the sample subjects was estimated to be 63.5%. Disease activity, measured objectively with erythrocyte sedimentation rate (ESR) and subjectively by duration of morning stiffness, was a major incentive for adherence to the treatment regimen. Among subjects with active disease (ESR greater than 20 mm in 1 h), the rate of compliance was 73.8%, but this fell to 52.7% among those with a normal ESR (i.e. ESR less than or equal to 20 mm in 1 h). The motivations and perceptions of the subjects concerning their drug therapy also affected compliance. Compliance was however less dependent on perceptions when active inflammation was present.