The significance of mucinous carcinoma has been controversial since first described by Parham in 1923. Previous reports have suggested that mucinous tumors affect young patients, involve the more proximal colon, are more advanced at diagnosis, and have a poorer prognosis than nonmucinous colon carcinoma. More recent reports have refuted these results. In an effort to clarify the significance of mucinous histology, a retrospective review of cases of invasive colon cancer treated at the Ochsner Clinic between 1982 and 1985 was undertaken. Mucinous adenocarcinoma, as defined by > or = 50 percent mucin, was found in 52 patients. During the same period, 343 nonmucinous adenocarcinomas were resected. The mean age, distribution within the colon, stage at diagnosis, and survival of mucinous carcinoma patients were compared with those with nonmucinous tumors. Mucinous tumors presented at a statistically significant more advanced stage (38 percent vs. 22 percent Dukes C lesions; P < 0.01). No significant differences were seen in age at presentation, distribution within the colon, or stage-for-stage survival when the entire group was analyzed. Mucinous carcinomas of the rectum occurred at an advanced stage more frequently (P < 0.05) than nonmucinous rectal carcinomas and had a markedly worse five-year survival (11 percent vs. 57 percent; P < 0.002).