Increased calcium intake from dairy products has been suggested as a risk factor for prostate cancer. We propose that the high dietary phosphate of dairy products may more readily explain this risk rather than the increased calcium. Several epidemiologic correlations have indicated an increased risk of prostate cancer with long-term, high intake of dairy products in male U.S. physicians and males in Sweden. This relation has been mechanistically associated with the higher dietary intake of calcium in dairy products. We propose, however, that the high dietary phosphate of dairy products affects much larger fluctuation in serum phosphate and may be a more likely source of prostate cancer risk from high dietary intake of dairy products.