Tonsils were obtained from 50 children suffering from recurrent tonsillitis. The tonsils' core material was cultured for aerobic and anaerobic microorganisms. Beta lactamase production was assayed in all isolates and beta lactamase activity was measured in the contents of each tonsil. Mixed aerobic and anaerobic flora was obtained in all patients, yielding an average of 7.9 isolates (4.4 anaerobes and 3.5 aerobes) per specimen. Beta lactamase production was noted in 58 isolates recovered from 39 tonsils (78%). These were all 21 isolates of S. aureus and 10 B. fragilis, 18 of 45 B. melaninogenicus (40%), 7 of 14 B. oralis (50%), and 2 of 13 H. influenzae type B (15%). Beta lactamase activity was detected in 33 of the 39 (85%) tonsils which harbored beta lactamase-producing bacteria, and in none of the 11 tonsils which had no beta lactamase-producing bacteria. Our findings indicate the polymicrobial nature of deep tonsillar flora in children with recurrent tonsillitis, and demonstrate the presence of detectable beta lactamase activity in the tonsillar tissue in most of the tonsils which harbored beta lactamase-producing organism.