AIM: To investigate an extent of smooth muscle differentiation of pericryptal fibroblasts. METHODS: Expression of high molecular weight caldesmon (h-CD) and alpha smooth muscle actin was investigated in 123 invasive colorectal adenocarcinomas and their surrounding non-neoplastic tissues. RESULTS: The monoclonal antibody to h-CD, which showed predominantly positive immunostaining in well differentiated smooth muscle cells, recognised pericryptal fibroblasts, smooth muscle cells, and pericytes, but was not reactive to myofibroblasts. Antibody to alpha smooth muscle actin recognised not only pericryptal fibroblasts, smooth muscle cells, and pericytes but also myofibroblasts. CONCLUSIONS: Pericryptal fibroblasts show greater smooth muscle differentiation than myofibroblasts and there is a possibility that they are well differentiated smooth muscle cells; h-CD is an excellent marker to discriminate pericryptal fibroblasts from myofibroblasts.