The symptoms of fungal infections of the nasal sinuses aren't typical, and often are confused with bacterial infections. The aim of study is to present the case of fungal infection in the maxillary sinus as a complication of endodontic treatment in upper second left premolar. The factors and mechanism which have influence on development of fungal infection in the maxillary sinus was presented in the discussion

Key words: Aspergillosis, maxillary sinus, endodontic treatment.