In order to learn about the influence of dietary factors and obesity on prostatic cancer in our environment, a case-control study was performed. The group of cases consisted of 90 men histologically diagnosed with prostatic cancer in the 'La Paz' hospital (Madrid) during the 4-year period of 1983-1987. The controls were 180 men selected to obtain a random sample of males from the same hospital, stratified according to age and date of admission as compared with the prostatic cancer patients. The results of the study revealed that a diet rich in animal fats as well as high in meat consumption increased the risk of prostatic cancer. Low ingestion of vitamin A or vitamin C and obesity were unassociated to the disease.