The prognostic significance of cathepsin-D expression was evaluated by immunohistochemistry in 638 node-positive breast carcinomas diagnosed between 1980 and 1986. A minimum of 2.5 years of follow-up was available for each patient (maximum: 9.5 years). Cathepsin-D expression was assessed separately both in cancer and in stromal cells using a commercially available polyclonal antibody. While cancer-cell immunostaining was not associated with prognosis, positive staining of stromal elements was related to shorter metastasis-free survival. The difference in distant metastasis-free survival between positive and negative expressors was greatest in the sub-group of patients submitted to adjuvant chemotherapy, with a hazard ratio for occurrence of distant metastasis of 1.76 by multivariate analysis, but was lowest for those receiving hormone therapy. Cathepsin-D expression by stromal cells was related to HER-2/neu oncoprotein expression, HSP-27 expression, poor nuclear grade, aneuploidy, and absence of estrogen and progesterone receptors. No association was found with the number of involved lymph nodes, tumor size, age, histologic grade, S-phase fraction, or vascular invasion. Our study suggests that cathepsin-D expression by stromal cells (and not by cancer cells) affects the prognosis of breast cancer, that stromal cells probably play a key role in local invasion and metastatic dissemination of the tumor, and that the prognostic significance of cathepsin-D expression may vary according to the type of adjuvant therapy.