Three consecutive cases of severe aplastic anemia undergoing immunosuppressive therapy with cyclosporin A (CyA) and high-dose methylprednisolone (HDMP) developed grand mal seizures after receiving ketoconazole treatment. All the seizures were reversed after transient discontinuation of those drugs. To our knowledge, it has not been reported as yet that the combination of ketoconazole and HDMP may considerably increase the risk of CyA-induced seizure. We would advise that ketoconazole and HDMP not be taken concomitantly with CyA treatment, and whenever ketoconazole therapy is needed, CyA be started with as small a dose as possible.