Acne is the most common skin disorder in the United States. Although many cases are transient, the condition is often chronic, causing self-consciousness and social stigmatization over the short term and physical scars and damaged self-esteem over the long term. Patients and clinicians have frequently attributed acnegenesis to diet; studies of varying quality have been published on the topic since the 1830s. Recently, well-designed, controlled, prospective studies suggest an acnegenic effect of specific dietary factors, including high-glycemic-index foods and dairy products. Limited evidence also suggests an acnegenic effect of foods containing saturated fats. More well-designed, randomized, controlled trials are needed to further establish dietary effects on acne. Based on epidemiologic observations and results of prior clinical trials, we are conducting a pilot study to determine if a low-fat, low-glycemic-index vegan diet affects the number of acne lesions and acne severity.