Aerobic bacterial examination for sinusitis was conducted using specimens from maxillary sinuses collected by antral puncture in 540 patients--284 men and 256 women aged 6-89 years--between May 1999 and April 2000. We obtained 528 strains of bacteria. Our results were as follows: 1. We obtained 303 pathogens from 540 patients. In acute sinusitis, the most frequently found was Streptococcus pneumoniae (30.4%), followed by Hemophilus influenzae (27.7%). In chronic cases, the most frequently found was Streptococcus pneumoniae (16.0%), followed by Hemophilus influenzae (15.1%) and Staphylococcus epidermidis (12.6%). 2. We found an increase in bacteria resistant to multiple drugs, with 11.1% of the Staphylococcus aureus isolates methicillin-resistant in acute sinusitis and 40% methicillin-resistant in chronic sinusitis, and that 30.6% of Streptococcus pneumoniae isolates were penicillin-resistant. 3. Ciclacillin was effective against 64.7% of all pathogens isolated in this study, cefpodoxime proxetil effective against 6.5%, and cefixime effective against 2.4%. 4. In considering pathogens, we therefore choose antibiotics and make a maxillary aspiration puncture.