Expression of HMGI(Y), a nucleoprotein that binds to A/T rich sequences in the minor groove of the DNA helix, is observable in neoplastically transformed cells but not in normal cells. We have analyzed HMGI(Y) expression in colorectal cancer and evaluated its clinicopathologic significance. HMGI(Y) mRNA was measured by CRT‐PCR (competitive reverse transcription‐polymerase chain reaction). Immunohistochemical staining for HMGI(Y), p53 and Ki‐67 was performed in the same colon cancer tissues, and the results in colorectal tissues were similar to those of RT‐PCR. HMGI(Y) expression evidenced by RT‐PCR was observed in 63 of 64 (98.4%) colorectal cancer samples, and 2 of 5 (40%) adenomatous polyps, whereas 21 normal colon samples were negative (p<0.001). High HMGI(Y) expression using CRT‐PCR was found in colon cancers with a high Ki‐67 labeling index (p<0.001). There was no significant correlation between the levels of HMGI(Y) expression and stage, tumor size, lymph node metastasis, histologic grade and immunohistochemical status of p53. Our results indicate that the HMGI(Y) expression may occur at an early stage of carcinogenesis and correlate with cell proliferation. Int. J. Cancer (Pred. Oncol.), 84:376–380, 1999. © 1999 Wiley‐Liss, Inc.