We have investigated some possible risk factors for cutaneous warts in a consecutive group of renal transplant recipients treated with three different immunosuppressive regimens: prednisolone + azathioprine (PA), predniso- Ione + azathioprine + cyclosporin (PAC), prednisolone + cyclosporin (PC). Kaplan and Meier analysis showed an earlier onset of warts in the PAC and PC groups than in the PA group (p < 0.0001), which might be related to the different immunosuppressive action of the pharmacological treatments including cyclosporin. Seven patients had skin cancer: 4 ofthem also had multiple warts on the cancer site. In 2 patients, histological examination demonstrated the neoplastic transformation of a wart. Maintenance posology of azathioprine, cyclosporin and prednisolone may be an important risk factor for cutaneous warts; on the other hand HLA-B mismatch and HLA-A11 seem to have no effect.