Cyclosporine microemulsion (CsA) has been the mainstay immunosuppressive agent for renal transplant recipients (RTR) for years. Single daily dosing of cyclosporine (SD) is rarely used. To evaluate the efficacy of SD versus twice daily dosing of CsA in RTR. etrospective evaluation of SD use was conducted for 44 RTR for 12 months (study group). Equal numbers of matched RTR were selected for age, sex, HLA mismatch, donor type, and immunosuppressive regimen (control group). CsA trough (C0) and peak (C2) blood levels, 12-hour CsA profile, and the area under the concentration-time curve (AUC) were measured. There were significant differences in C0, C2 and calculated AUC after shifting to SD (p<0.0001, <0.0001 and 0.004) respectively. In the study group, the mean AUC was 4619 ng/mL/hour before versus 6567 ngmLhour after shifting to SD. This became more therapeutic and identical to the mean AUC in the control group which was 6551 ng/mL/hour. Total daily CsA dose was lower in the study group when compared with the control group at 6 and 12 months (p<0.0001). There were significantly fewer adverse effects in patients in the study group than in patients in the control group. There were no significant differences in rejection rate, graft and patient outcome between the groups. CsA dose should be individualized in RTR. Single daily dosing of CsA has the added advantage of decreasing dosages and cyclosporine-related adverse effects while maintaining optimal graft function