We have reviewed 44 mucinous intestinal (MI) and 10 mucinous mullerian (MM) tumors of low malignant potential (LMP) seen at The George Washington University Medical Center. As previously reported by Rutgers and Scully, MMLMP tumors occurred in younger women, were generally smaller and more frequently bilateral, had a papillary rather than multicystic appearance, and lacked goblet cells. All patients with MMLMP tumors were recurrence-free at last follow-up, including three whose tumors were microinvasive. Patients with MILMP tumors also all did well regardless of tumor grade, with the exception of a single patient with bilateral grade 1 ovarian tumors, an appendiceal villous adenoma, and pseudomyxoma peritonei. Microinvasion was also seen in four of these tumors, none of which recurred. Review of the literature suggests that MILMP tumors without stromal invasion but with either prominent cell stratification or marked nuclear atypia may have a worse prognosis than those lacking these features, but probably largely because of a correlation with higher stage disease. We believe that tumors of this sort should not be diagnosed as "noninvasive carcinomas," but should be sectioned more extensively for evidence of stromal invasion and subjected to careful staging. If the tumor is still noninvasive and in stage I after these procedures, the likelihood of treatment failure appears to be in the range of 1-3%.