Collagenolytic enzymes produced by tumor cells are believed to play a significant role in the destruction of surrounding normal tissue and, in certain experimental animal systems, the ability of tumor cells to degrade type-IV collagen (basement membrane collagen) correlates positively with those cells' metastatic capacity. We measured collagenolytic activity levels of extracts from freshly excised colorectal carcinoma tissues and of conditioned media from primary organ culture (total of 114 tissues from 53 patients) by using purified radiolabelled type-I (rat tail) and type-IV (mouse Engelbreth-Holm-Swarm [EHS] sarcoma) collagens. Both type-IV and type-I collagenolytic activity levels of extracts from tumor and adjacent mucosa ranged from less than 1 to 80 ng/hr/mg wet tissue, and no significant differences between mucosa and carcinoma tissues were observed. In conditioned media, the type-IV collagenolytic activity was low for normal mucosa and benign tumors and slightly higher for carcinoma than for mucosa. In 5 of 32 primary tumors, collagenolytic activity levels were 2-5 times higher than in the rest of the tumors and mucosal tissues. There were no significant differences in collagenolytic activity levels of conditioned media and tissue extract from colorectal carcinoma of different Dukes' stages. Deep and superficial areas of primary tumors released similar type-IV collagenolytic activity levels, suggesting that there was little intratumoral heterogeneity in the release of this enzyme.