A main cause for gastrointestinal (GI) complications in graft recipients is the routinely administered inosine monophosphate dehydrogenase inhibitor mycophenolic acid (MPA). MPA is available in two formulations, the prodrug mycophenolate mofetil (MMF) and the enteric-coated sodium salt (EC-MPS). Clinical results point to a better GI tolerability of EC-MPS as compared to MMF. We performed an open surveillance study in 397 organ graft recipients to investigate the clinical tolerability of EC-MPS in renal graft recipients who were converted from MMF to EC-MPS (maintenance) or who received EC-MPS as a new component of their immunsuppressive regimen (de novo). Physicians recorded GI symptoms (nausea, emesis, anorexia, diarrhea, abdominal cramps) at the start of EC-MPS treatment (visit 1) and at the next two visits in the clinic (visits 2 and 3); general tolerability (very good/good/moderate/poor) was assessed at visit 2 and 3. Two hundred seventy-five patients were on maintenance treatment with MMF and were converted to equimolar doses of EC-MPS, and 122 patients received EC-MPS de novo. The mean time since transplantation was 4.2 +/- 4.4 years. Median time until visit 2 was 28 days and until visit 3, 65 days. In 63.0% of patients, tolerability was rated as very good at visit 2 and in 64.7% at visit 3. Most patients who had suffered from GI complications during preceding MMF treatment reported improvement or total disappearance of their symptoms after conversion to EC-MPS. In conclusion, EC-MPS is a useful means to reduce GI complications in MPA-treated patients.