The purpose of the study was to analyze the incidence of osteonecroses (ON) in systemic lupus erythematosus (SLE) patients with and without antiphospholipid syndrome (APS), primary APS (PAPS) and to define a relationship of the development of ON to some risk factors for vascular diseases. The study included 369 patients, including 293 with SLE, 160 with secondary APS, 76 with PAPS. The patients aged 14 to 63 years (mean 31.9+/-10.9 years). The history of disease was 0.6 to 30 years (mean 9.1+/-7.5 years). Among them 32 (8.7%) patients with aseptic necroses of different bones were selected in accordance with the data of X-ray studies. ON was detected in 8.7 patients with SLE and APS. The X-ray signs corresponded to third-to-sixth-degree ON. The most common site of ON was the head of the femur, although another site of ON was observed and multiple ON was typical. Leukopenia, creatininemia, fibrinogen levels were associated with ON (p < 0.05 by the Mann-Whitney test). The activity of SLE was significantly associated with SLEDAI scale scores (p < 0.05 by the Wald-Wolfovitz test). Six patients with SLE and ON had high scores by this scale--more than 40 scores of the maximum 150 possible scores. APS was diagnosed in 87.5 of the patients with ON (28 of the 32 patients) and only in 61.7% of the patients without ON (in 208 of the 337 patients) (chi2 = 8.4; p = 0.004). The development of ON in the examinees was significantly associated with the presence of APS. The activity of SLE, particularly nephritis, arthritis, positive tests for phospholipid antibodies, the presence of arterial thromboses, thrombocytopenia at the height of disease, therapy with large doses of glucocorticoids.