The following principles of appropriate antibiotic use for adults with acute pharyngitis apply to immunocompetent adults without complicated comorbid conditions, such as chronic lung or heart disease, and history of rheumatic fever. They do not apply during known outbreaks of group A streptococcus.1. Group A beta-hemolytic streptococcus (GABHS) is the causal agent in approximately 10% of adult cases of pharyngitis. The large majority of adults with acute pharyngitis have a self-limited illness, for which supportive care only is needed.2. Antibiotic treatment of adult pharyngitis benefits only those patients with GABHS infection. All patients with pharyngitis should be offered appropriate doses of analgesics and antipyretics, as well as other supportive care.3. Limit antibiotic prescriptions to patients who are most likely to have GABHS infection. Clinically screen all adult patients with pharyngitis for the presence of the four Centor criteria: history of fever, tonsillar exudates, no cough, and tender anterior cervical lymphadenopathy (lymphadenitis). Do not test or treat patients with none or only one of these criteria, since these patients are unlikely to have GABHS infection. For patients with two or more criteria the following strategies are appropriate: a) Test patients with two, three, or four criteria by using a rapid antigen test, and limit antibiotic therapy to patients with positive test results; b) test patients with two or three criteria by using a rapid antigen test, and limit antibiotic therapy to patients with positive test results or patients with four criteria; or c) do not use any diagnostic tests, and limit antibiotic therapy to patients with three or four criteria. 4. Throat cultures are not recommended for the routine primary evaluation of adults with pharyngitis or for confirmation of negative results on rapid antigen tests when the test sensitivity exceeds 80%. Throat cultures may be indicated as part of investigations of outbreaks of GABHS disease, for monitoring the development and spread of antibiotic resistance, or when such pathogens as gonococcus are being considered.5. The preferred antibiotic for treatment of acute GABHS pharyngitis is penicillin, or erythromycin in a penicillin-allergic patient.