OBJECTIVE Data from histopathological and migratory studies suggest that 1 or more late stage environmental promoters are involved in the development of clinical carcinoma of the prostate. Laboratory investigations and variously designed epidemiological studies in man have suggested that dietary fat may be one of these candidate tumor promoters but other studies have questioned this association. The biologically plausible associations that have been hypothesized include total energy consumption, altered androgen metabolism, oxidative stress, specific fatty acid consumption and pesticide intake. We provide a critical appraisal of the existing evidence for an association between dietary fat consumption and prostate cancer, and review the biologically plausible relationships. METHODS All 33 published case-control and cohort studies that examined the relationship between prostate cancer and dietary fat or specific fatty food types were critically appraised. Eight studies suggested a statistically significant association, and many studies noted significant associations for specific types of fatty foods (eg milk or meat) and prostate cancer. RESULTS In light of the inherent biases in the methodology of studying dietary fat intake and carcinoma of the prostate, we conclude that the evidence is consistent. CONCLUSIONS Corroborative studies in humans are required to better define this relationship. Prospective studies of dietary intervention should be encouraged.