INTRODUCTION: Truncal acne is often associated with facial acne, but there are fewer options for an effective topical treatment on the trunk. Given the advent of foam formulations with enhanced percutaneous absorption and convenient application due to easy spreadability on skin, the previously held idea that effective treatment of truncal acne requires oral treatment is challenged. Azelaic acid cream has been previously approved for acne vulgaris, thus azelaic acid foam may be a viable treatment option for truncal acne. STUDY DESIGN: A single-center, open label pilot study was conducted to investigate the efficacy and safety of azelaic acid 15% foam as a treatment modality for moderate truncal acne. Use for facial acne was also allowed and monitored during the study. RESULTS: Twice-daily application of azelaic acid 15% foam to affected areas resulted in a 1-grade reduction in truncal investigator global assessment (IGA) scores in nearly all patients (16/18). Eight out of 18 patients (44%) were rated as Clear or Almost Clear in the trunk by the end of the study. There were also improvements in facial IGA scores; 9 of 18 patients (50%) exhibited a 1-grade improvement in IGA scores and 11 of 18 were Clear or Almost Clear by the end of the study. A significant reduction in lesion counts was found throughout the study and the medication was well tolerated. CONCUSION: Azelaic acid 15% foam was effective in treating moderate truncal acne and facial acne in this pilot study. Given the efficacy and convenience of the foam vehicle, azelaic acid may be considered as a viable option for treatment of acne vulgaris, including on the trunk. Further studies are suggested in a larger population of patients, including adult females with acne. J Drugs Dermatol. 2017;16(6):534-538..