To assess the success of breast cancer control activities in Connecticut, we examined data from the Connecticut Tumor Registry, determining differences in breast cancer stage at time of diagnosis over time and in selected subgroups. From 1982 to 1985, the percentage of women with cancer confined to the breast increased from 54.0 percent to 61.3 percent. During 1984 and 1985, lower socioeconomic status (SES) women with breast cancer were less likely than higher SES women to be diagnosed with early-stage disease (56.9 percent vs 62.7 percent). SES was estimated by census tract of residence. In the same years, the overall incidence of breast cancer was greater in higher SES women. Projections based on these incidence data found that lower SES women, as compared to higher SES women, had a higher rate of expected breast cancer deaths (24.6 vs 19.7 per 100,000), and a greater percentage of those deaths considered preventable by early detection (22 percent vs 11 percent). The rate of preventable deaths in lower SES women was 2.5 times as great as that for higher SES women (5.3 vs 2.1 per 100,000). Tumor registries can serve as useful surveillance systems to aid cancer control programs. Breast cancer early-detection programs should give special attention to lower SES women.