The distribution and frequency of steroid hormone receptors are described in 329 patients with breast cancer. The distribution of each of the steroid hormone receptors is unimodal with a progressive increase in the proportion of patients positive at lower receptor values. Receptor values expressed as fmol/mg cytoplasmic protein are well correlated with values expressed as fmol/mg breast tumor. Estrogen receptor was positive in 53% of the patients; progesterone receptor was positive in 38% of the patients; glucocorticoid receptor was positive in 52% of the patients; and androgen receptor was positive in 31% of the patients. The type of tissue assayed did not affect steroid hormone receptor positivity. For primary tumors, there was no correlation between steroid hormone receptor positivity and location of the tumor in the breast, size of the tumor, or extent of the disease. Each of the steroid hormone receptors was positively associated with each of the other steroid hormone receptors. Estrogen receptor was correlated with menopausal status and axillary nodal status, but these correlations did not exist for the other steroid hormone receptors. Estrogen receptor was not correlated with age after adjustment for menopausal status. The other steroid hormone receptors were not correlated with age.