Ras oncogene mutations are found in a significant number of human colonic carcinomas. Correlation between patient survival and ras mutations was explored and compared with other clinical parameters. Colonic carcinoma embedded in paraffin was subjected to the polymerase chain reaction using primers to amplify codon 12 of the K-ras oncogene. Oligonucleotide probes to six mutations were used to identify mutated genes. A total of 71 cases were successfully amplified. Some 54% of the cases had mutations. There was no correlation between presence of a mutation and age. Patients in Stage D, patients with a family history of carcinoma, and males have a greater incidence of ras mutations. Patients in Stage C had a lower incidence of mutations. Presence of the mutation did not correlate with decreased survival except in Stage D. Some 61% of long-term survivors with colon carcinoma living for more than 6 yr had ras mutations. The absence of K-ras mutations did not identify long-term survivors.