A population-based, case-control study of prostate cancer in Utah was used to assess reported food-consumption patterns for the adolescent and adult years. Men reported eating eggs, whole milk, butter, white bread, cereals, and candy less frequently and red meat, fish, low-fat milk, cheese, yogurt, ice cream, margarine, fruits and vegetables, and wholewheat bread more frequently as adults, indicating that diets changed in the hypothesized direction to correspond to national changes in food-consumption practices. Men who consumed a diet high in saturated fatty acids as adults were at a slightly increased risk of developing aggressive prostate cancer after adjusting for adolescent diet (odds ratio 1.8 comparing high with low intakes), whereas men who consumed a diet high in saturated fatty acids as adolescents were not at increased risk of developing these tumors after controlling for a diet high in saturated fatty acids as adults (odds ratio 1.1).