Group A beta-hemolytic streptococcus can cause several postinfectious, nonsuppurative immune- mediated diseases including acute rheumatic fever, poststreptococcal reactive arthritis, pediatric autoimmune neuropsychiatric disorders, and poststreptococcal glomerulonephritis. Except for sporadic outbreaks, poststreptococcal autoimmune syndromes occur most commonly in sub-Saharan Africa, India, Australia, and New Zealand. Children younger than three years are rarely affected by group A streptococcus pharyngitis or rheumatic fever, and usually do not require testing. Rheumatic fever is a rare condition that presents as a febrile illness characterized by arthritis, carditis or valvulitis, and neurologic and cutaneous disease, followed many years later by acquired valvular disease. Recurrence rates are high. In addition to evidence of recent streptococcal infection, two major or one major and two minor Jones criteria are required for diagnosis. Electrocardiography, chest radiography, erythrocyte sedimentation rate, and an antistreptolysin O titer are the most useful initial tests. Echocardiography is recommended to identify patients with subclinical carditis. The arthritis usually responds within three days to nonsteroidal anti-inflammatory drugs. Poststreptococcal reactive arthritis is nonmigratory, can affect any joint, and typically does not respond to aspirin. Pediatric autoimmune neuropsychiatric disorders affect the basal ganglia and are manifested by obsessive-compulsive and tic disorders. The presentation of poststreptococcal glomerulonephritis ranges from asymptomatic microscopic hematuria to gross hematuria, edema, hypertension, proteinuria, and elevated serum creatinine levels.