Vital statistics show that a rise in incidence of endometrial cancer began in the mid-1960s on the West Coast of the United States. This rise was continuous and reached a peak in 1975. Elsewhere, incidence rates for endometrial cancer rose during the 1970s. It now seems evident that much of the rise in all areas of the country was due to replacement estrogen treatment. We estimated from data obtained from the Commission on Professional and Hospital Activities-Professional Activity Study of Ann Arbor, Michigan, that over 15,000 cases of endometrial cancer were caused by replacement estrogens during the five-year period 1971--1975 alone. This represents one of the largest epidemics of serious iatrogenic disease that has ever occurred in this country. With the substantial fall in estrogen sales starting in January 1976, there has been an associated decline in the incidence rates of endometrial cancer nationwide.
