Objective: To compare the efficacy and safety of a novel formulation of 15% azelaic acid gel (Finacea; Berlex Laboratories, Inc, Montville, NJ) with 0.75% metronidazole gel (MetroGel; Galderma Laboratories LP, Fort Worth, Tex) as topical therapy for moderate, papulopustular facial rosacea. Design: Multicenter, double-blind, randomized, parallel-group study. Setting: Thirteen US centers. Patients: A total of 251 patients with papulopustular rosacea with persistent erythema and telangiectasia. Interventions: Patients were randomized to receive azelaic acid gel or metronidazole gel twice daily for 15 weeks. Main Outcome Measures: Nominal and percent change in inflammatory lesion count, change in erythema and telangiectasia severity ratings, investigator's global assessment of rosacea, and investigator's and patient's overall improvement ratings. Results: Azelaic acid gel was superior to metronidazole gel in reduction of mean nominal lesion count (-12.9 vs -10.7, respectively) (P=.003) and mean percent decrease in inflammatory lesions (-72.7% vs -55.8%, respectively) (P<.001). With respect to erythema severity, 56% of azelaic acid gel-treated patients were rated improved vs 42% of metronidazole gel-treated patients (P=.02). The effectiveness of metronidazole gel on these variables seemed to plateau after week 8, whereas azelaic acid gel demonstrated progressive improvement through week 15. Neither treatment had a clinically appreciable effect on telangiectasia. Both the investigator's global assessment (P=.02) and overall assessment of improvement (P=.005) showed a significant therapeutic advantage for azelaic acid gel. Azelaic acid gel also scored higher on the patient's overall assessment of efficacy. Both treatments were rated as having high cosmetic acceptability. No serious or systemic treatment-related adverse events were reported in either group. Conclusion: Use of 15% azelaic acid gel twice daily for 15 weeks demonstrated significant superiority over using 0.75% metronidazole gel in improving principal signs of rosacea (inflammatory lesions and erythema).