To determine the risk of bacteremia during tonsillectomy, we cultured blood specimens that were taken from 32 children during surgery and tonsillar swabs that were obtained just before excision, and compared the results with quantitative cultures of the excised tonsillar tissue. Twenty-five children had Haemophilus influenzae within the tonsillar tissue (density range, 10(3) to 10(8) colony-forming units per gram), and seven had Streptococcus pyogenes (density, 10(3) colony-forming units per gram in one case, 10(5) colony-forming units per gram in one case, and 10(6) colony-forming units per gram in five cases). Twelve perioperative blood cultures were positive; H influenzae was found nine times, and Micrococcus species was found one time, and alpha-hemolytic streptococci were found two times. Haemophilus influenzae was always present in the corresponding tonsillar specimens, although there was no apparent relationship between the density of colonization of the tonsillar tissue and a positive blood culture.