Using the NIH 3T3 transformation assay system, an activated c-Ha-ras transforming gene has been identified in three distinct early passage colon carcinoma cell lines isolated from an invasive, differentiated, adenocarcinoma. The p21 c-Ha-ras gene product from these cell lines displayed an altered electrophorectic mobility and a point mutation in the DNA coding sequence leading to an amino acid substitution at position 12.