The objectives of the study were: (i) to compare the efficacy and safety of minimizing mycophenolate mofetil (MMF) early (30 d) or late (90 d) after renal transplantation, when used in combination with tacrolimus; (ii) to retrospectively investigate factors associated with early, acute rejections and (iii) to investigate the pharmacokinetic interaction between tacrolimus and diltiazem. A prospective, randomized, multicenter, open-label study was conducted in 124 de novo kidney transplant recipients. Efficacy and safety outcomes were assessed for 180 d after transplantation and subjects were followed-up for a mean duration of 5.1 yr. The efficacy and safety outcomes were comparable whether the dose of MMF was minimized early or late. The incidence of early, acute rejection episodes was higher for recipients who were younger, received a graft from an unrelated donor or failed to achieve adequate tacrolimus concentrations (trough > 10 ng/mL) in the first seven d after transplant. Concomitant use of diltiazem had a tacrolimus-sparing effect in some subjects. Based on these results, we support the achievement of a high target tacrolimus concentration within the first week after renal transplant and suggest that early minimization of MMF can be achieved when used in combination with tacrolimus.