Hemolytic uremic syndrome (HUS) has been reported in patients treated with cyclosporin A (CsA) following bone, hepatic and kidney transplantation. We report two patients with Behçet's disease (BD) under CsA treatment because of severe uveitis, who developed HUS several months after the initiation of treatment. Renal biopsies showed lesions consistent with the diagnosis of the arterial form of thrombotic microangiopathy: vascular thrombosis with extensive glomerular ischemia. Renal failure persisted after withdrawal of CsA: one patient is in chronic renal failure (CRF) with a 4-year follow-up; the other died after refusal of chronic hemodialysis. In our two patients, excessive doses of CsA with high trough levels are likely to have contributed to the development of HUS. A rapid adjustment of CsA doses and an early detection of signs of the microangiopathic process might have prevented this severe complication of CsA treatment.