A survey of 200 rheumatoid arthritis (RA) patients was conducted to identify the kinds and frequencies of intentional and unintentional reasons for missed medication dose. Planned and unplanned changes in usual activity routines accounted for most of the unintentionally missed doses, while side effects attributed to the medication accounted for most of the intentionally missed doses. Patients who did not miss medication doses were different from those who did by tending to have more financial resources and social support available to them.