• Time to relapse [ Time Frame: within 52 weeks ] [ Designated as safety issue: No ]
• Proportion of patients in endoscopical remission, defined as a mucosal appearance score of ≤ 1 at final/withdrawal examination. [ Time Frame: week 52 or premature withdrawal ] [ Designated as safety issue: No ]

This study intends to study the efficacy and tolerability of once daily 3.0 g mesalazine granules vs. once daily 1.5 g mesalazine granules vs. three times daily 0.5 g mesalazine granules for maintenance of remission in patients with ulcerative colitis

• Colitis, Ulcerative
• Recurrence

Inclusion Criteria:

• Signed informed consent,
• Men or women aged 18 to 75 years,
• Historically confirmed diagnosis of ulcerative colitis by endoscopy and histology,
• Patient being in remission, defined (according to Rachmilewitz) as:

Clinical Activity Index (CAI) <= 4, and Endoscopic Index (EI) < 4,

• Extent of inflammation during last acute episode was >15 cm beyond the anal margin,
• Last acute episode ended within 3 months prior to study entry.

Exclusion Criteria:

• Crohn's disease,
• Prior bowel resection leading to diarrhoea,
• Toxic megacolon,
• Gastric or duodenal ulcer,
• Haemorrhagic diathesis,
• Presence of symptomatic organic disease of the gastrointestinal tract (with the exception of haemorrhoids or hiatal hernia),
• Active colorectal cancer or a history of colorectal cancer,
• Serious other secondary illnesses of an acute or chronic nature,
• Asthma,
• Severe impairment of renal (e.g., serum creatinine > 1.5 mg/dl) and/or liver functions (e.g., serum transaminase [ALT and/or AST] or alkaline phosphatase >=2x upper limit of normal [ULN]),
• Application of immunosuppressants within 3 months and/or corticosteroids (oral, intravenous [IV] or topical rectal) within 30 days prior to baseline,
• Application of non-steroidal anti-inflammatory drugs (NSAIDs) as long term treatment (i.e. > 6 weeks), other than acetylsalicylic acid (<= 350 mg/day), or paracetamol,
• Known intolerance/hypersensitivity to salicylic acid and its derivatives or to any of the other constituents of the study drugs,
• Well-founded doubt about the patient's cooperation,
• Existing or intended pregnancy, breast-feeding,
• Women of child-bearing potential without adequate contraceptive protection, e.g., hormonal contraception, intrauterine device (IUD), double-barrier method of contraception (e.g., use of a condom and spermicide), partner has undergone vasectomy and subject is in monogamous relationship. The investigator is responsible for determining whether the subject has adequate birth control for study participation,
• Participation in another clinical trial within the last 30 days,simultaneous participation in another clinical trial, or previous participation in this trial.