Recurrence-free survival (RFS) has been evaluated with regard to estrogen and progesterone receptor (ER and PgR) status for 145 postmenopausal women with primary breast cancer at high risk for recurrent disease. All patients received only local-regional therapy as an adjuvant therapy (DBCG protocol 77-c patients). ER+ patients had a significantly longer RFS than ER-patients. This difference was apparent using a cut-off level of 10 fmol/mg cytosol protein to distinguish between ER+ and ER-patients. There was no apparent difference in patients with high (greater than = 100 fmol/mg cytosol protein) ER levels vs. those with intermediate (10-99 fmol/mg cytosol protein) levels, indicating that the prognostic value of ER determinations in the natural course of the disease resides in a qualitative rather than a quantitative distinction among patients. No difference in RFS was found patients when patient were subdivided according to PgR status. The clinical applicability of the ER-ICA assay method for ER determinations is demonstrated in a subset of patients, some of whom received adjuvant endocrine therapy.