Pretreatment sinus puncture was performed on 339 patients with acute community-acquired sinusitis (ACAS) between 1975 and 1990. Bacterial species recovered in titers of greater than or equal to 10(4) colony-forming units per milliliter (CFU/ml) from 383 sinus aspirates included Streptococcus pneumoniae, 92 (41%); Haemophilus influenzae, 79 (35%); anaerobes, 17 (7%); streptococcal species, 16 (7%); Moraxella catarrhalis, 8 (4%); Staphylococcus aureus, 7 (33%); and other, 8 (4%). Viruses (rhinovirus, parainfluenza virus, and influenza virus) and fungi (Aspergillus, zygomycoses, Phaeohyphomycis, Pseudallescheria, and Hyalohyphomycis) have also been reported to cause ACAS. Posttreatment sinus puncture was performed on 220 of the 339 patients in six studies to evaluate efficacy of selected antimicrobial agents in producing bacteriologic cure. Ampicillin, 500 mg four times daily; amoxicillin, 500 mg three times daily; trimethoprim-sulfamethoxazole, twice a day; cefaclor, 500 mg four times daily; bacampicillin, 800 mg twice a day; cyclacillin, 500 mg three times a day; cefuroxime axetil, 250 mg twice daily; amoxicillin-clavulanate, 500/125 three times daily; and loracarbef 400 mg twice daily, given in 10-day courses, produced bacteriologic cure in more than 90% of patients. Early studies were done before beta-lactamase-producing strains of H. influenzae were a frequent cause of ACAS in Charlottesville. Management of therapeutic failures is a difficult problem for which diagnostic and therapeutic sinus puncture and lavage, prolonged antimicrobial therapy, steroid therapy, and evaluation of allergy, immunodeficiency, and surgically correctable lesions of the osteomeatal complex are recommended.