Problem: The increase in retained mucus in chronic sinusitis is probably the result of poor ciliary activity and disorders in mucus production. The purpose of this study was to evaluate the changes in the ultrastructure of submucosal glands (SG) and globet cells (GC) after partial (around the ostium) or wide surgical removal of maxillary sinus mucosa (MSM). Methods: Twenty New Zealand white female rabbits were used. The rabbits were divided into 2 groups of 10. In group A the mucosa of the anterior cavity of the right maxillary sinus (MS) was completly removed without interfering with the ostium. In group B a strip of mucosa around the ostium was removed. After 3 months, the right and contralateral sinuses were opened again, in search of signs of infection. Bacteriological cultures were performed. The MSM was studied by light, scanning, and transmission electron microscopy. Results: After 3 months, in group A all right MS were infected with purulent secretions, and the SG with a mean value of 10.4 SG per mm, standard deviation (SD) 3.36, and GC 81.18 per mm (SD = 3.82). However, in group B the SG were 52.3 per mm (SD = 4.5) and GC 4.45 per mm (SD = 1.23). These results were statistically significant ( P < 0.001). Histopathological findings showed in group A; after 3 months, SG altered with a fewer number of secretory granules and a fewer number of microvilli in the glandular lumen. Conclusion: In rabbits after wide mucosal removal of MSM there was a marked decrease in the number of SG and increased density of GC, which might be expected to result in increased mucus viscosity and decreased mucus production. Significance: In functional endoscopic sinus surgery, partial or selective removal of mucosa near the ostium may allow regeneration of more normal SG and GC without disorders in mucus production. Support: None reported.