BACKGROUND The locus and extent of resection and the type of reconstruction used in surgery are important joint determinants of functional outcome in oral and oropharyngeal cancer patients. However, prediction of functional outcome from broader factors such as clinical T stage and approximate locus of resection is important for the preoperative period when the extent of resection and the exact surgical reconstruction to be used may not be decided and preoperative counseling about potential functional outcomes is needed. METHODS Oropharyngeal swallow efficiency (OPSE) and conversational speech understandability (CU) were measured preoperatively and 3 months posthealing in 68 patients. Analysis of variance (ANOVA) was used to determine whether clinical T stage and planned surgical locus were significantly related to these two functional measures, and discriminant analysis was used on the data obtained at 3 months to determine how well CU and liquid OPSE jointly relate to the T stages. RESULTS In patients with a planned oral tongue locus of resection, significant differences were found at 3 months posthealing on both CU and liquid OPSE between stages T1 -T2 and T3 and between T1-T2 and T4. In patients with a planned oropharynx locus of resection, significant differences were found only on CU at 3 months. These occurred between T1-T2 and T4 and between T3 and T4. Discriminant analysis classified into the correct T stages 70% of T1-T2 and 75% of T4 stage patients, but only 28% of T3 stage patients. However, the T3-stage patients who were misclassified as T4 had significantly larger mean percent of oral tongue resected than those T3 stage patients who were misclassified as T1-T2. CONCLUSIONS These results are useful for the preoperative counseling of patients with clinical T stages 1-2 and 4. The relationship between T stage and postsurgical function found here is stronger than reported by previous authors, but is still very general.