The role of mammography as an effective means of early detection of breast cancer is well established. Needle localization of occult tumors under mammographic guidance has become the principle method of sampling impalpable breast lesions. As a result, the number of clinically inapparent breast carcinomas sampled has increased rapidly. Under these circumstances, as a result of the size and the nature of these "early carcinomas," it may not be possible to assess the hormone receptor expression of these tumors by conventional biochemical assay and/or immunocytochemical analysis. To determine the usefulness of imprint preparation for detecting hormone receptors, 214 examples of primary, recurrent, and metastatic breast cancers were studied. Immunostaining of imprint preparations with monoclonal antibodies against the estrogen (H222SPy) and progesterone receptors (KD68) showed a high degree of concordance with immunocytochemical assay and biochemical analysis done on frozen tissue of the same tumors. This technique can be done easily and is well suited for tumors that are too small and/or ill defined to permit separate sampling for hormone receptor analysis.