The incidence of cyclosporine (CsA) vascular toxicity is open to debate. We attempted to evaluate the incidence of hemolytic accidents in our series of patients taking all clinical forms into consideration. From January, 1989, to December, 1990, 117 patients received kidneys from cadaver donors and were treated with CsA. Five patients presented hemolytic uremic syndrome (HUS) accompanied by a rejection crisis; 6 patients presented hemolytic anemia associated in 2 cases with marked thrombocytopenia without any evidence of rejection. Cytomegalovirus (CMV) infection was diagnosed in 2 patients and bacterial infection preceded hemolysis in 2 other cases, suggesting a triggering factor. In addition, when we systematically determined haptoglobin levels after introduction of CsA treatment, we found asymptomatic hemolytic episodes more frequently. Our incidence of hemolytic accidents was approximately 10%. Hemolysis could indicate ischemic vascular damage leading to arteriolar medial hyalinosis preceding fibrosis in CsA nephrotoxicity. Thus, it would be interesting to detect asymptomatic forms of hemolysis by monitoring haptoglobin levels. This approach could lead to a reduction of the CsA dose in patients presenting low haptoglobin levels, even in the absence of evidence of nephrotoxicity.