20% azelaic acid cream was compared clinically with its vehicle in a 3-month double-blind study of 92 patients with moderate inflammatory acne. It was found that the azelaic acid treatment significantly reduced inflamed and non-inflamed lesions and yielded clinically relevant improvement rates. Its action was significantly more effective than its vehicle. In the study of comedo acne, 20% azelaic acid cream was equally effective as 0.05% tretinoin cream in reducing the number of comedones and with respect to overall response. However azelaic acid cream was better tolerated, causing fewer local side effects than the tretinoin.