The immunohistochemical expression of the extracellular matrix (ECM) components tenascin (TN), fibronectin (FN), collagen type IV (Coll) and laminin (LN), and their possible relationships were studied in a series of 134 operable breast cancer cases. Their expression was also compared with the expression of the proteolytic enzyme cathepsin D (CD), the adhesion molecule CD44 standard form (CD44s) and other known factors to clarify the prognostic value and role of these molecules in tumour progression and metastasis. TN expression in the tumour stroma was positively correlated with tumour grade and size, CD44s expression, tumour and stromal CD expression as well as with FN, laminin and Coll expression in the same areas. TN expression was inverse correlated with ER status. Its expression at the invasion front was only positively correlated with the lymph node status. Survival analysis showed an increased mortality risk associated with high levels of TN expression. In multivariate analysis, among the ECM proteins, only TN expression was independently correlated with patients' survival. FN expression was positively correlated with lymph node involvement, with the proliferation-associated index Ki-67 and stromal CD expression. Survival analysis showed an increased mortality risk associated with a high level of FN expression. Coll expression was positively correlated with the tumour size and LN expression. An inverse relationship of Coll expression with ER and PgR receptor status was also found. LN expression was positively correlated with tumour and stromal CD expression, with the proliferation-associated index Ki-67 and inversely with ER receptor status. The observed alterations in the expression of ECM proteins in breast cancer tissue and their correlations with the proteolytic enzyme CD and the adhesion molecule CD44s, suggest an involvement in cancer progression. In addition, overexpression of stromal TN and FN seems to have negative prognostic value in breast cancer patients.