Estrogen (ER) and progesterone (PgR) receptors were measured simultaneously in 1144 consecutive breast cancer patients to determine the distribution of patients according to receptor and menopausal status when receptor occurrence rates were considered. The prognostic significance of PgR, either alone or in association with ER, was studied on 187 consecutive breast cancer patients treated only by radical mastectomy. All the cases, as regards axillary node status, were pathologically assessed as node negative. These patients did not receive any adjuvant treatment after mastectomy. At 36 months after mastectomy, the follow-up indicated that PgR- patients have a worse prognosis than PgR+ ones. This is evident when PgR alone is considered as a prognostic factor as well as when it is used to identify, within ER+ cases, those with a higher probability of relapse. In conclusion, it can be stated that although PgR status is an independent prognostic factor, it is useful to evaluate ER and PgR simultaneously for better patient management.