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, 1200 patients with a recent history of squamous cell and/or basal cell carcinoma will be enrolled at six participating centers over a four-year period and will be randomly assigned to either 0.1% tretinoin cream or placebo. They will be followed for a minimum of two years to determine if topical tretinoin is effective in reducing the risk of new occurrences.