Neoral is a microemulsion formulation of cyclosporin (CyA), which has more consistent and better pharmacokinetics parameters with improved bioavailability compared to conversional formulation of Sandimmune. Sixty-four stable adults (age >18 years), who had received liver transplants (LTx) and were on Sandimmune-based immunosuppression, were converted to Neoral on milligram for milligram basis. Mean age was 52.5 +/- 13.5 years and male/female distribution was 22/42. Mean interval from LTx to conversion was 109.2 +/- 136 months. In 13 patients (20%) the dose of Neoral was reduced because of an increase in serum creatinine (N = 9), hyperkalemia (N = 1), headache (N = 1), peripheral parasthesia (N = 1), and a general sense of discomfort (N = 1). Interestingly, in two patients a decrease in the trough concentration was observed with the increase in liver enzymes. Both patients responded to an increase in Neoral dose. The present study suggests while the majority of the stable liver transplant patients (77%) can be safely converted to Neoral from Sandimmune on a milligram to milligram basis, they need to be carefully monitored for renal function, liver function, and trough concentration of CyA.