The estrogen receptor status in 335 primary breast carcinomas was correlated with disease-free interval, survival and site of recurrent disease. Estrogen receptor positive carcinomas had a longer disease-free interval, a longer survival (mastectomy-death) and a longer time interval between recurrence and death. These parameters were also influenced by the lymph node status at mastectomy. Estrogen receptor positive cancers had a significantly better chance of survival independent of lymph node status. Estrogen receptors also delayed recurrence in node-positive carcinomas, but this advantage gradually disappeared with increasing interval after mastectomy. Estrogen receptor positive or estrogen receptor negative primary carcinomas did not show any predilection for spread to any particular site.