One-third of all malignancies in the United States (approximately one million cases diagnosed annually) are nonmelanoma skin cancer (NMSC). NMSC causes considerable morbidity, economic burden, facial deformity and at least 1,000 deaths annually. Prevention of these malignancies with a topical agent free of serious side effects would confer substantial public health benefit. Three hundred fifty thousand veterans were expected to develop NMSC in 1994. NMSC is one of the most common conditions requiring dermatologic care in the VA system. Topical tretinoin has been used extensively to treat photoaged skin. Retinoids administered orally in high doses appear to be effective in chemoprevention of nonmelanoma skin cancer but have unacceptable toxicity. In this study, 1131 patients with a recent history of squamous cell and/or basal cell carcinoma were enrolled at six participating centers over a four-year period and were randomly assigned to either 0.1% tretinoin cream or placebo. They were followed for a minimum of two years to determine if topical tretinoin is effective in reducing the risk of new occurrences.