We aimed to improve symptoms by means of mesalazine in symptomatic colonic diverticular disease patients. One hundred seventy outpatients (98 M, 72 F; age, 67.1 years; range, 39-84 years) were assigned to four different schedules: rifaximin, 200 mg bid (Group R1: 39 pts), rifaximin, 400 mg bid (Group R2: 43 pts), mesalazine, 400 mg bid (Group M1: 40 pts), and mesalazine, 800 mg bid (Group M2: 48 pts), for 10 days per month. At baseline and after 3 months we recorded 11 clinical variables (upper/lower abdominal pain/discomfort, bloating, tenesmus, diarrhea, abdominal tenderness, fever, general illness, nausea, emesis, dysuria), scored from 0 = no symptoms to 3 = severe. The global symptomatic score was the sum of all symptom scores. After 3 months in all schedules but Group R1, 3 of the 11 symptoms improved (P < 0.03); the global score decreased in all groups but Group R1 (P < 0.0001). Mesalazine-treated patients had the lowest global score at 3 months (P < 0.001). Mesalazine is as effective as rifaximin (higher dosage schedule) for diminishing some symptoms, but it appears to be better than rifaximin for improving the global score in those patients.