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 whole-wheat 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).