Colorectal cancer initiation and progression are associated with stepwise genetic alterations. We and others have shown that a gene encoding for a 32-kDa putative laminin-binding protein (LBP-32) is overexpressed during colorectal cancer progression by Northern blots analysis. Northern blots cannot indicate the heterogeneity of expression from cell to cell and the distribution pattern of gene expression within a given tumor. In order to overcome these problems, we examined the LBP-32 mRNA expression in colorectal carcinomas by in situ hybridization. LBP-32 mRNA expression in 30 cases of primary and metastatic colorectal cancers and their respective adjacent normal tissues were detected by in situ hybridization using 35S-UTP radiolabeled antisense riboprobes. The results showed that LBP-32 mRNA was expressed at a low level in the normal colonic mucosa adjacent to the tumor compared with colon cancer tissues. Its expression in poorly differentiated colorectal cancer was much higher than that in well- and moderately differentiated colorectal cancer. More importantly, the LBP-32 mRNA was expressed more highly in the invasive lesions of the cancer and liver metastases compared with the cancer lesions in situ. Our results imply that in situ hybridization is a powerful tool in evaluating the changes in gene expression in the cancer cells and LBP-32 mRNA expression is related to progression, invasion, and metastasis of colorectal cancer.