The objective of this study was to assess the efficacy and safety of moxifloxacin versus amoxicillin-clavulanate plus roxithromycin (comparator) in adult community-acquired pneumonia (CAP) patients with risk factors. In this comparative, randomized, multicenter, open-label study, patients hospitalized for CAP received a 10-day oral treatment with either moxifloxacin (400 mg o.d.) or amoxicillin-clavulanate (1,000/125 mg t.i.d.) plus roxithromycin (150 mg b.i.d.). Clinical and bacteriological outcomes were assessed during test of cure and follow-up visits (5-7 days and 21-28 days after the end of treatment, respectively). Of 349 randomized patients, 346 were included in the intent-to-treat analysis and 289 in the per-protocol analysis. Their baseline characteristics were comparable. The most frequent risk factors for mortality were age >65 years (50.0%), alcoholism (23.1%), and comorbidities (50.6%); chronic obstructive pulmonary disease (COPD) (25.4%) and diabetes mellitus (13.6%) were the most common associated comorbidities. A causative pathogen was documented in 66 of 346 (19.1%) of the patients (including 21 with positive blood cultures). Respective per-protocol clinical success rates at test-of-cure (primary efficacy endpoint) for moxifloxacin and comparator were 131 of 151 (86.8%) and 120 of 138 (87.0%), with a 95% confidence interval (CI) of -8.0-7.6 for the difference. Bacteriological success rates (eradication) were 23 of 30 (76.7%) and 23 of 31 (74.2%); rates for patients with positive blood cultures were 10 of 14 and 4 of 6. Persistent clinical success rates at follow-up were 118 of 120 (98.3%) and 102 of 106 (96.2%), with a 95%CI of -2.2-6.4 for the difference. The intent-to-treat analysis confirmed these results. Adverse events associated with moxifloxacin and the comparator drug were reported for 42 of 171 (24.6%) and 50 of 175 (28.6%) of the patients, respectively, and comprised predominantly digestive disorders, which occurred in 9.4% and 21.1%. On the basis of these results, once-daily oral moxifloxacin alone is as effective as amoxicillin-clavulanate plus roxithromycin for the treatment of CAP in patients with risk factors.