Preoperative cytologic diagnosis of the maxillary sinus was performed on 57 patients by examining of solutions obtained by local washing following sinus puncture. There were 6 cases of cancer (5 squamous cell carcinomas and 1 adenoid cystic carcinoma), 1 malignant melanoma, 1 odontoma, 8 aspergillosis, 1 inflammatory pseudotumor, 9 odontogenic maxillary sinusitis and conventional chronic sinusitis in residual cases. There were 2 false-negative cytologies in the 7 cases of malignant tumor (i.e., 1 adenoid cystic carcinoma and 1 squamous cell carcinoma). The significance and usefulness of the cytologic approach to preoperative diagnosis of malignancies, including malignant melanoma and fungal infection were discussed.