OBJECTIVE: To raise the main microbiological founds in 10 patients who had evolved after maxillary sinusitis to be operated for surgeon-dentists. MATERIAL AND METHODS: They had been directed for bacteriological and fungal inquiry the content of the maxillary sinus of 10 submitted sinusotomy patients to maxillary endoscopic for treatment of maxillary sinusitis. They had been directed for bacteriological and fungal inquiry the content of the maxillary sinus of 10 submitted patients to maxillary sinusotomy endoscopic for treatment of the maxillary sinus. When evolving maxillary sinusitis had been dealt with by the surgeon-dentists with antibiotic therapy without improvement the signals and symptoms and thus directed for specialist in Otolaryngologist. RESULTS: The findings had been of a polymicrobial, composed infection for aerobics and anaerobic. In the acute cases pneumoniae had predominance of Streptococcus, Haemophilus influenzae, Prevotella sp., Peptostreptococcus sp. e Fusobacterium sp. Already in the chronic cases streptococcus - hemolytic, Microaerophilic had predominated streptococci, Staphylococcus aureus, Prevotella sp., Peptostreptococcus sp. an Fusobacterium sp. In 2 cases with chronic evolution they had been identified the presence of Aspergillus to Niger. CONCLUSION: In the case maxillary sinusitis the knowledge of the microbiology is important in the definition of therapeutical with antimicrobials and/or the surgery of these patients.