BACKGROUND: Combination therapy with a topical retinoid and an antibiotic is recognized as a rational and effective approach for the treatment of acne vulgaris. Adapalene, a naphthoic acid derivative with anti-inflammatory and receptor-selective retinoid properties, is safe and well tolerated. While the combination of adapalene with oral or topical antibiotics has been shown to deliver a superior and faster response than an antibiotic alone, the clinical benefits of a combination of adapalene and doxycycline, the most frequently prescribed oral antibiotic for acne in the United States, have yet to be evaluated. OBJECTIVE AND METHODS: In a 12-week study, the efficacy and safety of the combination of adapalene gel 0.1% with doxycycline was compared with doxycycline alone for the treatment of severe acne. Subjects were randomized to receive doxycycline once daily in the morning and either adapalene or vehicle once daily in the evening. RESULTS: At Week 12, the combination adapalene-doxycycline was significantly superior to doxycycline alone for change from baseline in total (p<0.001), inflammatory (p=0.02), and noninflammatory (p<0.001) lesions. Significant differences in total lesions were observed as early as Week 4 (p=0.04). Both treatments were well tolerated, and no serious adverse events were reported. CONCLUSIONS: The study demonstrates that the combination of adapalene and an oral antibiotic provides a superior and faster benefit than antibiotic therapy alone and should be considered at the initiation of treatment.