Background: Hormone receptor (HR) expression has prognostic and predictive significance in breast cancer. Most HR-positive tumors are ER positive (ER+). In contrast, tumors that are ER negative (ER-) and PgR positive (PgR+) are uncommon and may represent an analytic artifact. We have previously shown that ER-/PgR+ tumors have been associated with younger age, higher grade, and Her2/neu over-expression suggesting a distinct biologic entity (Proceedings 103^rdUSCAP Meeting). Here we evaluated clinical outcomes of ER-/PgR+ breast cancers. Methods: We retrospectively reviewed a well-characterized database comprising 816 sequential patients diagnosed with early stage invasive breast carcinoma in Salamanca, Spain. Outcomes of interest were time to relapse (TTR) and overall survival (OS). Multivariable Cox proportional hazards analysis was conducted to assess the association of ER-/PgR+ with TTR and OS in comparison to ER+ and to ER- and PgR negative (ER-/PgR-) tumors. Results: Fifty-six patients (7%) had ER-/PgR+, 624 (77%) had ER+ and 136 (17%) had ER-/PgR- phenotypes. For ER-/PgR+, ER+ and ER-/PgR- tumors, five-year relapse rates were 36%, 20% and 42%, and five-year OS was 92%, 93% and 66%, respectively. ER-/PgR+ showed annual hazards of relapse that were intermediate between ER+ and ER-/PgR- patients. Relapses occurred early in follow-up for ER-/PgR+ and ER-/PgR- tumors with few relapses beyond year 6. ER+ tumors showed a continuous risk of relapse throughout follow-up. Multivariable analysis for TTR is shown in the Table. Only nodal status and receptor group were associated with worse OS. Conclusions: ER-/PgR+ tumors are a rare, but defined subgroup. They have a higher risk of relapse than ER+ tumors, but lower than ER-/PgR- tumors. The timing of relapse more closely resembles ER-/PgR- disease, whereas overall survival more closely resembles ER+ disease. Further research on the role of PgR in breast carcinogenesis is warranted.