A total of 102 cases of undifferentiated carcinoma of nasopharyngeal type (UCNT) were reviewed to attempt their classification into histologic forms of different prognosis. Each slide reviewed was evaluated for predominant tumoral tissue architecture, and the quality, amount and topography of the stroma. Immunoperoxidase studies in 80 cases allowed definition of the immunologic profile of the lymphoplasmocytic stroma. For equivalent clinical stages, the different histologic types are defined as a function of the architecture: cordonal or diffuse, compact or fragmented; these forms, when combined with cytologic characteristics and quality of stroma distinguished 3 microscopic groups of different evolution. The fragmented diffuse forms appear to have the best prognosis (85.5% survival at 5 years), the compact cordonal forms the worse prognosis (13.2% survival at 5 years): the intermediate or diffuse compact forms were of fair prognosis (42.8% survival at 5 years). Application of histology to determine prognosis of UCNT should allow future adaptation of treatment (radiotherapy and/or chemotherapy) to each case.