A retrospective analysis of 21 male and 82 female patients with systemic lupus erythematosus (SLE) was performed in order to identify sex-linked differences in disease manifestations. As organ manifestation, cardiac involvement was assessed in 12 of 21 male patients (57%) and in 18 of 82 females (22%; p < 0.05). Renal involvement occurred in 16 male (76%) vs 26 female patients (32%; p < 0.05). Endstage renal disease developed in 5 of the 21 men (24%), but only in 6 of the 82 women (7%) with SLE. The most striking clinical result was the high frequency of thrombembolic complications in male SLE-patients. Twelve out of 21 males (57%) experienced more than 30 thrombembolic events in contrast to 9 events in 5 out of 82 females (6%; p < 0.0001). Persisting elevated IgG-anti-cardiolipin antibodies were found in 48% of male and only 16% of female patients (p < 0.05). In conclusion, these data suggest that SLE in males is characterized by more frequent and severe organ involvement and especially by striking prevalence of partly life-threatening thrombembolic complications.