This study assessed self-reported adherence in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) from underserved healthcare settings. We conducted a cross-sectional survey of 102 ethnically diverse patients--70 with RA and 32 with SLE--attending rheumatology clinics at publicly funded hospitals in Houston, Texas; 43% were Hispanic, 32% African-American, and 25% White. Treatment adherence was evaluated using the compliance questionnaire rheumatology (CQR; 0, low adherence and 100, high adherence) and the questionnaire of the Adult AIDS Clinical Trials Group (AACTG). The patients were also asked how often they forgot to take their prescribed medications or discontinued them on their own. Mean patient age was 48.5 years; 75% were female, 32% were African-American, 43% Hispanic, and 25% White. Only one third reported never forgetting to take their medications; 40% reported having stopped their medications on their own because of side effects, and 20% because of lack of efficacy. Mean CQR score was 69.1 +/- 10.5, suggesting moderate adherence overall. Differences were also observed across ethnic groups: 23% of ethnic minority patients had problems taking their medications at specified times compared to 11% of Whites (p = 0.03). Lower education and side effects were associated with lower adherence. No differences were observed between RA and SLE patients. Many patients with RA and SLE report problems with treatment adherence. These appear to be more prevalent in African Americans and Hispanics than Whites; the impact of decreased adherence on outcomes could be significant and should be considered when treating patients with RA and SLE.