Enteric-coated mycophenolate sodium (EC-MPS) is an enteric-coated formulation of mycophenolic acid. A 12-month, multicenter, double-blind, randomized clinical study demonstrated that converting maintenance renal transplant patients from mycophenolate mofetil (MMF) to EC-MPS is safe and does not affect efficacy. In an open-label study extension, 130 patients initially randomized to MMF were converted to EC-MPS (newly exposed); 130 initially randomized to EC-MPS continued on EC-MPS (EC-MPS long-term). A composite endpoint of biopsy-proven acute rejection (BPAR), graft loss, or death occurred in 3 (2.3%) newly exposed and 2 (1.5%) EC-MPS long-term patients during the extension phase. One patient died and one lost his graft. BPAR occurred in 3 (2.3%) newly exposed patients and 1 (0.8%) EC-MPS long-term patient. During the first 12 months of the extension phase, incidence and type of adverse events was similar in both groups and comparable to that seen in the core study. Nine cases of malignancy were reported, mainly nonmelanoma skin cancers. EC-MPS dose adjustments for adverse events were required in <12% of patients. At the end of the 12-month extension, 58 (44.6%) and 64 (49.2%) newly exposed and EC-MPS long-term patients, respectively, had reported at least one gastrointestinal adverse event. Mean serum creatinine remained stable at the 12-month visit of the extension study (137 micromol/L in the newly exposed and 142 micromol/L in the EC-MPS long-term groups). The results of this study demonstrate the long-term safety of EC-MPS and reconfirm the safety of converting MMF maintenance renal transplant patients to EC-MPS.