Previous human studies in renal transplant recipients have shown a lower incidence of acute rejection and cyclosporine-associated acute nephrotoxicity when prostaglandins are administered in conjunction with standard immunosuppressants. This study evaluates the effects of enisoprost (EP), a synthetic PGE methyl ester analog, in a single-center, prospective, randomized, double-blind, placebo-controlled, parallel group trial in 81 consecutive adult patients undergoing orthotopic liver transplantation (OLT). The subjects received EP 100 mg p.o. t.i.d. (n = 40) or placebo (n = 41) for the first 12 weeks after OLT. Immunosuppression was based on cyclosporine, azathioprine, and corticosteroids. Effective renal plasma flow and glomerular filtration rate were determined at 4 and 12 weeks after OLT. Eighty-one patients entered the study; sixty-six patients completed the 16-week study period. There were no statistically significant differences between EP- and placebo-treated groups at 12 weeks for creatinine clearance, glomerular filtration rate, and effective renal plasma flow. At least 1 episode of cyclosporine nephrotoxicity occurred in 7/40 patients (17.5%) in the EP group compared with 9/41 patients (20.0%) in the placebo group (P = 0.781). There was no significant difference in the incidence of graft rejection episodes in the 2 groups. Enisoprost, as used in this study, does not have any beneficial effect on renal function or incidence of rejection in OLT recipients.