A subgroup of patients with childhood-onset obsessive-compulsive disorder (OCD) and/or tic disorders has been identified who share a common clinical course characterized by dramatic onset and symptom exacerbations following group A beta-hemolytic streptococcal (GABHS) infections. This subgroup is designated by the acronym PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections). There are five clinical characteristics that define the PANDAS subgroup: presence of OCD and/or tic disorder; prepubertal symptom onset; sudden onset or abrupt exacerbations (relapsing-remitting course); association with neurological abnormalities (presence of adventitious movements or motoric hyperactivity during exacerbations); and temporal association between symptom exacerbations and GABHS infections. In this subgroup, periodic exacerbations appear to be triggered by GABHS infections in a manner similar to that of Sydenham's chorea, the neurological variant of rheumatic fever.