To verify the prognostic value of the histological typing of intestinal-type adenocarcinoma (ITAC) of the sinonasal tract, 41 such lesions were separately classified by 2 pathologists both according to the World Health Organization (WHO) criteria for the histological typing of large intestine adenocarcinomas (well, moderately, poorly differentiated adenocarcinomas, and mucinous adenocarcinomas) and to the criteria of Kleinsasser and Schroeder (papillary-tubular cylinder cell type, alveolar-goblet cell type, signet-ring cell type, and transitional type). Using the WHO classification, 7 adenocarcinomas (17.1%) were well differentiated, 15 (36.6%) were moderately differentiated, and 6 (14.6%) were poorly differentiated; 13 cases (31.7%) were classified as mucinous adenocarcinoma. Following the Kleinsasser and Schroeder classification, 28 adenocarcinomas were of the papillary-tubular cylinder cell type (PTCC), 6 tumors (14.6%) were of the alveolar-goblet cell type (AGC), 1 (2.4%) was of the signet-ring cell (SRC) type, and 6 (14.6%) were of the transitional (TR) type. The interrater agreement in subtyping for both histological classifications was 92.6% (kappa, 0.89; P < .001). Kaplan-Meier analysis of cases stratified according to WHO classification showed that patients with mucinous and poorly differentiated adenocarcinomas had a significantly shorter disease-free interval and survival rate than patients with well and moderately differentiated adenocarcinomas (P = .02 and P < .001, respectively; log-rank test). Separate evaluation of survival for patients with AGC and TR adenocarcinomas did not show any statistically significant difference (P = .5). Clinical stage was advanced in most cases (92.6% of patients had T3 or T4 carcinomas) and had no prognostic relevance in the current series, as did treatment and occupational exposure. We conclude that the histological typing of ITACs is highly reproducible and appears to be related to the clinical outcome of the tumors. Adenocarcinomas with a prominent (>50%) mucinous component tend to have a similar clinical behavior, irrespective of their cyto-architectural features and the presence of an associated tubulopapillary component. Therefore, the separation into alveolar-goblet, signet-ring, and transitional forms has no prognostic impact.