Experimental studies suggest that both quantity and quality of dietary lipid can influence the developmental course of several major forms of cancer -- notably skin, mammae, and intestine. For some cancers, epidemiological data support these studies and demonstrate a positive correlation between dietary fat intake and mortality rates. Until the current clinical trial, the relationship of diet to skin cancer had received little attention. The specific aim of this proposal is to provide definitive and statistically sound evidence, in a close-controlled clinical setting, as to the ability of a low-fat dietary intervention to alter the course of non-melanoma skin cancer development. 70 skin cancer patients presenting with a non-melanoma skin cancer (basal or squamous cell carcinoma), but having had not more than two previous ones, will undergo a series of laboratory and base-line evaluations. Upon qualification, the 70 patients will be randomized into two groups of 35 each. One group will be in a control in which no changes in dietary habits will be introduced. The remaining group (Dietary Intervention, DI) will adopt a diet characterized by reduced fat intake (20% of total caloric intake). Both groups will be examined at 4 months intervals, over 24 months, for non-melanoma skin cancer occurrence. In addition, the DI group will be evaluated monthly for dietary compliance and reinforced with respect to dietary goals. Laboratory tests will be completed at designated intervals to detect any adverse side-effects of the low-fat diet. Based upon data obtained from 116 patients completing the ongoing study, power calculations indicate that an additional 70 patients will provide significant (P<0.01) evidence with statistical probability of 80% that a low-fat diet reduces non-melanoma skin cancer incidence. The additional patients will provide not only definitive evidence for the involvement of dietary lipids in skin cancinogenesis, but will avail an effective means for the prevention and management of this highly prevalent form of cancer.