We examined the frequency, reasons and outcome after conversion from Tacrolimus to Cyclosporine A. From August 1989 to December 1992, 1000 consecutive liver transplantation patients were studied, which included 834 adults (age>18 yr.) and 166 children with mean follow-up of 77 months (range 56 to 96). A prospectively populated electronic database was queried to identify patients that underwent conversion, the clinical indication and outcomes. Thirty-seven out of 834 adult recipients (4.43%), mean age of 48.4+/-12.9 years, 19 male (51.35%) and 18 females (48.64%) required conversion from Tacrolimus to Cyclosporine A baseline immunosuppressive therapy. No pediatric patient required conversion. The mean time interval from liver transplantation to Cyclosporine A conversion was 443.45+/-441.44 days (range 22 to 1641). The clinical indications for conversion included: 20 neurological (54%), 6 gastrointestinal (16%), 5 hematological (14%), and 6 other (16%) scenarios. Seven of the 37 patients (18.9%) died. The causes of death were multi-organ failure (2), sepsis (2), pancreatitis (1), hepatic failure due to relapse of ethanol abuse (1), and unknown cause (1). Nine out of 37 patients (24.32%) had to be reconverted to Tacrolimus (mean 282.22+/-499.79 days; range 15 to 1583 day with a median of 135) after institution of Cyclosporine A; none showed recurrence of the original symptoms. The reasons for these re-conversions were acute cellular rejection (44%, n=4), chronic rejection (11%, n=1), increased hepatic enzymes (33%, n=3) and progressively worsening neurological symptoms (11%, n=1). The frequency of conversion from Tacrolimus to Cyclosporine A was 4.43%. Conversion is safe and efficacious if done in a controlled setting. Additionally, re-conversion to Tacrolimus for lack of efficacy of Cyclosporine A did not appear to be associated with a recurrence of the condition that caused the initial switch.