A series of 258 breast cancer patients with known estrogen receptor (ER) status of the primary tumour who subsequently developed metastases were reviewed for site of first metastasis. In 188 cases progesterone receptor (PgR) data were also available. Univariate analysis showed metastatic patterns to differ statistically significantly related to ER status and (less pronounced) PgR status of the primary tumour. Patients with ER-positive tumours had bone metastases three times more often than patients with ER-negative tumours. With respect to PgR-positive and PgR-negative tumours this frequency differed by a factor of two. With regard to visceral metastases ER and PgR status were equally potent prognosticators, patients with receptor negative tumours having a 50% higher frequency of visceral metastasis than patients with receptor positive tumours. Assessment of metastatic patterns in relation to combined receptor status did not substantially enhance the discriminatory value of ER and PgR when assessed separately. Multivariate analysis showed that the observed differences in metastatic patterns were all attributable to differences in the ER status of the primary tumour, and were not influenced by age, menopausal status, axillary lymph node involvement, duration of disease-free interval (DFI), mode of postoperative treatment, or the PgR status of the primary tumour.