Objective information on arthritis drug compliance in usual care settings is sparse. Of "causes" of poor compliance, regimen complexity has received special attention. We used a previously validated pharmacy-based compliance measure to study compliance in an arthritis clinic. Across drugs, mean compliance was low (64%). Wide variations were seen among drugs, ranging from 55% mean compliance (indomethacin) to over 80% (prednisone, penicillamine). Major variations by diagnosis were also found, with rheumatoid arthritis patients more compliant than others. Regimen complexity was a relatively weak correlate of compliance, and the overall level of arthritis drug compliance was similar to that reported for antihypertensive drugs.