Infantile bilateral striatal necrosis (IBSN) is characterized by a dystonic movement disorder and basal ganglia imaging abnormalities. Acute IBSN often occurs after upper respiratory tract infections although no specific micro-organism which may cause IBSN has been identified. We present 2 children (1 year 2 months and 4 years) with acute IBSN after clinical pharyngitis. Both IBSN patients had serological evidence of recent beta-haemolytic streptococcal infection. Due to the association of post-streptococcal disorders with anti-basal ganglia antibodies (ABGA), we examined both patients for anti-neuronal antibodies. For comparison, 20 children with dystonia (9 females, 11 males; mean age 4 years 1 month), and 20 children with uncomplicated streptococcal infection (12 females, 8 males; mean age 5 years 9 months) were examined. Both IBSN patients had antibodies reactive against basal ganglia constituents of molecular weight 40 kDa. Immunohistochemistry showed antibody reactivity against large striatal neurons only. Other anti-neuronal antibodies were negative, supporting striatal specificity. All controls were negative for ABGA. Acute IBSN is part of the post-streptococcal autoimmune neuropsychiatric spectrum. An autoimmune aetiology should be considered in this phenotype, as immunomodulatory therapies may reduce morbidity and mortality.