Sore throats are most commonly due to infections, many of which are viral and do not require specific treatment. Symptoms and signs of the common cold, influenza or croup, the occurrence of conjunctivitis in some adenoviral infections, generalised lymphadenopathy and splenomegaly in glandular fever or the presence of vesicles characteristic of herpangina (Coxsackie A virus) or of herpes simplex infection, occasionally enable a clinical diagnosis and avoid the need for antibiotic therapy. In the case of treatable conditions a typical membrane may suggest diphtheria, a scarlatiniform rash infection due toStreptococcus pyogenesor toCorynebacterium haemolyticum, and a cherry-red epiglottisHaemophilus influenzaetype b. Associated atypical pneumonia suggests infection withMycoplasma pneumoniaeorChlamydia pneumoniae. Pharyngitis due toNeisseria gonorrhoeaemay be accompanied by infection at other sites or by other sexually transmitted diseases. Candidal infection, in the appropriate clinical circumstance, should suggest HIV infection. Surgical drainage is required in the case of peritonsillar or retropharyngeal abscess. Noninfectious cases of sore throat, e.g. thyroiditis, are relatively uncommon considerations in the differential diagnosis of acute febrile pharyngitis. The most common problem is to recognise streptococcal pharyngitis, which requires antibiotic treatment for 10 days to avoid the risk of rheumatic fever.