This population-based study presents trends in the treatment of node-negative invasive carcinoma of the breast in females during the 1980s in the Detroit metropolitan area. It was done to determine whether or not there has been a significant shift toward conservation of the breast from 1980 to 1987. Trend analyses of surgical treatment, tumor size, node status, year of diagnosis, age and race were performed for 13,217 patients drawn from the Metropolitan Detroit Cancer Surveillance System. A significant increase in the use of conserving the breast was observed, with younger women receiving this treatment option more often than older women. Implications for a continuing shift in the biologic findings and treatment of carcinoma of the breast are discussed.