We compare the results of 2 different strategies for the management of patients with uncomplicated left colonic diverticulitis and to analyze differences in quality of life and economic costs. The most frequent standard management of acute uncomplicated diverticulitis still is hospital admission both in Europe and United States. This multicenter, randomized controlled trial included patients older than 18 years with acute uncomplicated diverticulitis. All the patients underwent abdominal computed tomography. There were 2 strategies of management: hospitalization (group 1) and outpatient (group 2). The first dose of antibiotic was given intravenously to all patients in the emergency department and then group 1 patients were hospitalized whereas patients in group 2 were discharged. The primary end point was the treatment failure rate of the outpatient protocol and need for hospital admission. The secondary end points included quality-of-life assessment and evaluation of costs. A total of 132 patients were randomized: 4 patients in group 1 and 3 patients in group 2 presented treatment failure without differences between the groups (P=0.619). The overall health care cost per episode was 3 times lower in group 2, with savings of €1124.70 per patient. No differences were observed between the groups in terms of quality of life. Outpatient treatment is safe and effective in selected patients with uncomplicated acute diverticulitis. Outpatient treatment allows important costs saving to the health systems without negative influence on the quality of life of patients with uncomplicated diverticulitis. Trial registration ID: EudraCT number 2008-008452-17.