To statistically evaluate the factors that influenced speech following maxillectomy, the speech intelligibility (SI) in 54 patients was measured with and without a prosthesis. The mean SI score without a prosthesis in all patients was 35.7 +/- 22.7% and that with a prosthesis was 84.9 +/- 12.7%. The results of the postmaxillectomy SI statistical analysis revealed that an oro-nasal communication was one of the factors that influenced SI without a prosthesis. The resection of the anterior portion of the soft palate was one of the factors that influenced SI with a prosthesis, which suggested that for some of these patients we should consider specific surgical treatment, aimed at the reconstruction in the deep defect extending to the intratemporal fossa. A new classification of maxillary defects has been proposed which will help to predict the grade of post-maxillectomy speech disorder following surgery.