Evidence from recent studies in several laboratories indicates a relationship between type or level of fat in the diet and occurance of tumor at specific sites. The essential fatty acids in fat and degree of their unsaturation are important to determine the influence of a dietary fats on carcinogenesis. Alteration of dietary fat can also change carcinogenesis of cell in several tissues. Dietary fats appear to be important in both initiation and promotion stages of carcinogenesis. Several possible mechanisms have been investigated how dietary fat could affect to carcinogenesis at cellular level. One potential mechanism of dietary fat on carcinogenesis is through modulation of protein kinase C activity in the cell.