Patients with amyloidosis secondary to familial Mediterranean fever (FMF) are known to tolerate cyclosporin A poorly. We report a case of severe cyclosporin toxicity in a patient with FMF amyloidosis who underwent kidney transplantation. The clinical syndrome consisted of severe gastrointestinal, neuromuscular, and psychiatric disturbances. Histological examination of the transplanted kidney revealed vasculitis of the polyarteritis nodosa type. We hypothesize that FMF patients are more vulnerable to the acute vascular toxicity of cyclosporin due to defective inhibition of complement activation, leading to a widespread vasculitis of the polyarteritis nodosa type.