Cyclosporine G (OG 37-324) reportedly is an efficacious immunosuppressant with less nephrotoxicity than cyclosporine A. This is a prospective randomized double-blinded trial comparing cyclosporine G and cyclosporine A in cadaveric renal transplantation. Patient and graft survival, as well as major infectious complications, were not different between the two groups. Objective parameters of renal function, including serum creatinine, creatinine clearance, and inulin clearance, were routinely performed. These generally demonstrated less nephrotoxicity in those patients treated with cyclosporine G compared with cyclosporine A. Minor elevations of alanine aminotransferase were noted in the cyclosporine G-treated patients but this was not associated with acute morbidity. Overall, cyclosporine G appears to be equally as effective as cyclosporine A, but demonstrated notably less nephrotoxicity.