Laminin, type IV collagen and fibronectin were examined immunohistochemically in the invasive component of breast carcinomas. Laminin was expressed around the invasive carcinoma cell nests in 38 (54%) of 71 cases. Immunoreactivity for type IV collagen was observed around the invasive carcinoma cell nests or the stroma apart from carcinoma cells in 44 (80%) of 55 cases. Fibronectin was strongly expressed in the stroma only in 75 (99%) of 76 cases. The expression of laminin significantly correlated with tubular formation in the invasive carcinoma cell nests and showed a tendency to be correlative to estrogen receptor (ER) and progesterone receptor (PgR) of carcinoma tissue, but no correlation among laminin expression, histological type, the age of patients, tumor size and lymph node metastasis was noted. Type IV collagen and fibronectin did not correlate to any clinicopathological factors such as histological type, grade of differentiation, the age of patients, tumor size, lymph node metastasis, ER and PgR status. No concordant expression of these extracellular matrices was seen.