Poststreptococcal sequelae can be markedly reduced by antibiotic therapy which eradicates the organism from the pharynx. In a double blind study, the effectiveness of clindamycin palmitate liquid was compared with that of ampicillin for eradicating group A beta hemolytic streptococci from patients with pharyngitis. Cultures four days posttherapy were negative in 95 (93.2%) of 102 clindamycin treated patients and in 92 (87.6%) of 105 in the ampicillin group. Seventy-six clindamycin treated and 79 ampicillin treated patients had 28-day cultures with negative results in 69 (90.8%) and 67 (84.8%), respectively. Possible side effects were both mild and infrequent, 3.8 per cent from ampicillin and 2.6 per cent from clindamycin. It was concluded that clindamycin palmitate is palatable, relatively free of side effects and is an effective drug for treatment of streptococcal pharyngitis. No poststreptococcal sequelae occurred.