Messenger RNA levels of the c-fos, c-myc, c-Ha-ras and c-Ki-ras genes were studied in 39 tissue samples obtained from 17 patients undergoing surgery for colon carcinoma and other colon diseases. DNA extracted from the same samples was studied by Southern analysis. The tissues were tumors and grossly normal mucosa from each case and in some instances benign polyps and metastases. Our results indicate: (1) that 50% of cases studied show an increase in expression of at least one of the oncogenes studied; (2) that over-expression is not random, some cases over-expressing several of the genes studied; (3) that the expression pattern of the oncogenes studied varies between primary tumor and metastases; (4) that amplification is a rare event, being limited to one instance in which c-myc was amplified in a metastasis; (5) that cases which exhibit high levels of mRNA in one or more genes studied correlate with biologically aggressive tumors; and (6) that "non-expressors" are at higher risk for local recurrence based on correlations with mucin histochemistry.