Myositis is a rare but recognized complication of systemic lupus erythematosus (SLE). This study compares clinical and laboratory features in patients with SLE complicated by myositis with patients with SLE who do not have myositis. Thus we reviewed the notes of 10 patients with an overlap of biopsy-proven myositis and SLE and compared their clinical, serological and immunogenetic features with 290 patients with SLE without myositis. Our data suggests that patients with SLE associated with myositis are more likely to have alopecia, oral ulcers, erosive joint disease and pulmonary disease but less likely to have renal disease. Our SLE/myositis patients were likely to die at a younger age. The overall disease process seems to be influenced by the presence of anti-RNP autoantibodies.