By using mRNA differential display technology, we have identified three cDNA clones, myl 3, myl 4, and myl 6, to show significant changes in expression between human colorectal tumor and paired normal tissue. Northern blot analysis indicated that clone myl 3 expression was elevated in normal tissue, and clone myl 4 expression was elevated in tumor tissue. Nucleotide sequence analysis revealed that clones myl 3 and myl 4 have not been previously identified. However, clone myl 6 appears to be the human homolog of the 3' end region of tissue inhibitor of metalloproteinase 3 (TIMP-3). Northern blot analysis showed that a 2.5 kb TIMP-3 transcript was expressed at a much higher level in normal tissue than the colorectal tumor.