Lower prevalence of non-reproductive system cancers among former college athletes. Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 250-253, 1989. The prevalence (lifetime occurrence) rates of cancers of nonreproductive organs and tissues were determined for 5,398 living alumnae, 2,622 of whom were former college athletes and 2,776 who had been nonathletes, from data on medical history, reproductive history, athletic training, and diet. The non-reproductive system cancers were divided into two classes: class I, which included cancers of the digestive system, thyroid, bladder, lung, and other sites and hematopoietic cancers (lymphoma, leukemia, myeloma, and Hodgkin's disease), and class II, which included skin cancers and cutaneous melanoma. The former college athletes had a significantly lower prevalence of class I cancers compared to the nonathletes; the age-adjusted relative risk (RR) equals 3.34, 95% confidence limits (1.35, 8.33), P = 0.009. In contrast, the prevalence rates of malignant melanomas and skin cancers did not differ significantly between the former athletes and nonathletes. The age-adjusted RR did not differ from 1.0. The lower prevalence rate of class I cancers among the former athletes is in accord with previous findings of a significantly lower prevalence rate of breast cancer and cancers of the reproductive system among former college athletes compared to nonathletes.