Fifty-five outpatients with acute tonsillitis and/or pharyngitis due to group A beta-hemolytic streptococci were treated during 1978 and 1979. Twenty-nine patients received 400 mg of bacampicillin twice a day, 21 patients received 250 mg of penicillin V four times a day, and five patients received 250 mg of amoxicillin every 8 hr. All except one patient, who was treated with bacampicillin, had a satisfactory clinical response to treatment. The bacteriologic response was satisfactory in all but one patient. None of the 55 patients developed adverse effects that necessitated the discontinuance of the antibiotic in use. No significant differences were found between the clinical or the bacteriologic responses to bacampicillin, penicillin V, or amoxicillin (Fisher's exact test).