Relationships between certain histopathologic features of tumor specimens and estrogen receptor (ER) status were investigated. Lobular and ductal carcinomas were found to be richer in ER than other histologic types. Well differentiated carcinomas were more often hormone receptor positive than poorly differentiated tumors. Lymphocytic and plasmatocytic infiltration in and around the tumor as well as elastosis also appeared to be related positively to ER status.