The clinical and bacteriologic aspects of chronic sinusitis in childhood were studied. Of 35 children who underwent surgical procedures for chronic sinusitis, 22 had positive bacteriologic cultures of aspirates from the sinus. The most common organisms isolated were Haemophilus influenzae, Streptococcus pneumoniae, and Branhamella catarrhalis. Five of eight S pneumoniae strains were relatively resistant to penicillin and resistant to sulfamethoxazole-trimethoprim. All of the B catarrhalis and 20% of the H influenzae organisms were beta-lactamase positive. Overall, 14 of 28 of the bacteria were penicillin resistant. In addition, all 12 children 2 years of age or younger had a positive bacterial culture as compared with much lower rates in older children. Although the incidence of S pneumoniae strains that are relatively resistant seems to be rising, to our knowledge we report the first description of these organisms as significant pathogens in chronic childhood sinusitis. These results indicate that chronic, difficult to manage sinusitis in very young children is frequently bacterial in origin, especially if the patient is 2 years old or younger. In light of the frequent failure of antibiotic therapy and considering the incidence of relatively resistant S pneumoniae strains, puncture of the sinus should be considered early in the course of chronic sinusitis to isolate pathogenic organisms and determine appropriate antimicrobial therapy.