Objectives: Once-daily formulation of tacrolimus has begun to find a place in daily clinical practice as similar efficacy and safety profile as the twice-daily formulation according to clinical trials. However, few numbers of un-sponsored, non-trial studies are issued centering on its usage in clinical practice. We compared once-daily and twice-daily formulation of tacrolimus in terms of the efficiency and effects on graft function in de novo kidney transplant patients.Methods: Twenty once-daily (TAC-OD) and twenty twice-daily (TAC-BID) tacrolimus administrated de novo kidney recipients who had received initial immunosuppressive therapy according to protocols at our institution (0.2 mg/kg of tacrolimus combined with 1000 milligrams of steroid taper plus 720 mg of mycophenolate and with 2,5mg/kg human immune globulin) assessed in terms of demographics, drug doses and blood concentration, and graft function. Results: The mean tacrolimus blood concentration measurements were higher in the TAC-OD group in the first sixty days after transplantation, and the TAC-OD group showed more blood concentration overshoots in the first 30 days of the treatment. The initial drug dose was significantly higher in the TAC-OD group compared to the TAC-BID group (p=0.04). There was no meaningful difference among groups according to graft function (creatinine measurements) (p>0.05).Conclusion: Between de novo kidney recipients, the new TAC-OD formulation presents a similar short-term efficacy profile as TAC-BID. However, a higher daily dosage of TAC-OD is needed to achieve similar blood concentrations in the early postoperative period.