Human epidermal growth factor (EGF) and DNA ploidy patterns were investigated in order to elucidate malignant potential of 216 surgically resected colorectal carcinomas. EGF positive was detected in 140 out of 216 (64.8%) cases and DNA aneuploidy was found in 137 out of 216 (63.4%). No significant correlations were recognized between EGF expressions and DNA ploidy patterns. We subclassified the cases into four groups according to their histological EGF expressions and DNA ploidy patterns. In these groups, the relationship among EGF expressions, DNA ploidy patterns and clinicopathological findings was studied. Subgroups had a significant relation to depth of invasion, lymph node metastasis, lymphatic invasion and clinical stage. In patients with curative operation, the prognosis was significantly lower in EGF-positive-DNA aneuploidy group than in EGF-negative-DNA diploidy group. In DNA diploidy, the prognosis of EGF-positive group was poorer than in the EGF-negative group. In conclusion, the EGF expression as well as DNA ploidy patterns may be useful to assess malignant potential in colorectal carcinoma.