Twenty-five liver transplant patients were administered liquid microemulsion cyclosporine (Neoral, 5 mg/kg b.i.d.) via a nasogastric tube until they could take oral medication. The first dose was given within 6 hr after surgery. Adequate trough levels of cyclosporine were obtained from the first postoperative day. The total exposure to the drug was low on the first postoperative day, but a significantly improved pharmacokinetic profile with a high maximal concentration and a low time to maximal concentration was found from the second postoperative day. The absorption from Neoral increased during the first week. After 1 week, a low within-patient variation coefficient for dose-adjusted cyclosporine trough levels was found (17%). The between-patient variation coefficient was low during the whole postoperative period (31%). We conclude that in liver transplant patients adequate immunosuppressant blood levels of cyclosporine can be obtained in the immediate postoperative period using Neoral without the need to go to the intravenous form of the drug.