Patients with systemic lupus erythematosus often assess their disease activity differently from their physicians. We studied the factors associated with this discordance. The data provided by 534 systemic lupus erythematosus patients were analyzed. We compared the physician and patient assessments of lupus activity on a visual-assessment scale from the same visit. We collected clinical data and scores from MOS 36-Item Short-Form Health Survey, Systemic Lupus Erythematosus Quality-of-Life Questionnaire, Rheumatology Attitudes Index, Systemic Lupus Erythematosus Disease Activity Index, and revised Systemic Lupus Activity Measure. Patients tended to score their disease activity higher than do their physicians, when these factors were present: poorer general health assessment, presence of thrombocytopenia, hypertension and urinary sediments, and difficulty in carrying groceries. Physicians tended to score the disease activity higher than do the patients in these circumstances proteinuria, hemolysis, use of azathioprine or cyclophosphamide, tiredness, photosensitivity, higher revised Systemic Lupus Activity Measure score, casturia, and patient report of being more easily ill than are other patients. There was only moderate correlation between the discordance in the baseline and the subsequent visits. The physician assessment of disease activity at baseline correlated better with an objective measure of disease activity (revised Systemic Lupus Activity Measure) in the subsequent visit than the patient assessment. In conclusion, discordance in the perception of disease activity between patients and physicians may be amenable to intervention.