OBJECTIVES: To assess the effect of conversion from MMF to EC-MPS on QoL in renal transplantation (RTx) recipients who need dose reduction due to GI symptoms.  METHODS: Multicenter, open-label, MMF-controlled, 12-weeks trial. RTx patients taking MMF who had previously reported GI adverse events were randomized to EC-MPS (n=70, equimolar dose for 0-2wk, dose optimization until maximum tolerated dose or 720 mg bid for 2-6wk and maintenance dose for 6-12wk); or continue MMF (n=64, same dose adjustment). Primary endpoint was Gastrointestinal Quality of Life Index (GIQLI); secondary endpoints were Gastrointestinal Symptom Rating Scale (GSRS), Psychological General Well-Being Index (PGWBI), Overall Treatment Effect (OTE) and optimization of doses of MPA. RESULTS: GIQLI scores were significantly better in EC-MPS groups at 12wk (110.1 vs 97.2 points, p=0.0136). Mean adjusted scores were also significantly in this group for all secondary scales used (GSRS: 36.3 vs 29.2 points, p=0.0017; PGWBI: 78.1 vs 72.4 points, p=0.0343). OTE evaluation of GI symptoms was significantly better for the EC-MPS group (p= 0.0145-patients and p=0.0006-physicians). The number of patients receiving intermediate doses of MPA (EC-MPS/720 mg - MMF/1000 mg) at 12 weeks was significantly higher in EC-MPS group (55.4% vs 27.4%, p=0.003). More patients with MMF were receiving low doses than with EC-MPS (35.6% vs 10.3%, p=0.0004). In MMF group a higher percentage of patients did not raise the dosage from baseline (23.5% for MMF and 8.9% for EC-MPS group, p=0.004).  CONCLUSIONS: EC-MPS improves gastrointestinal quality of life in renal transplant patients with GI complaints to MMF, as it allows an optimization of MPA dose without increasing GI-related symptom burden.