The objectives of our study were to examine the sera of rheumatic chorea (RhCh) patients (those with acute or chronic RhCh or with a past history of RhCh) for the presence of antineuronal antibodies (ANeurA) and to correlate the results with disease activity, chronicity, and the number and durations of choreic attacks. Subjects were inpatients of the Pediatric Hospital, Ain Shams University, and outpatients of the Outpatient Pediatric Cardiology Clinic (both in Cairo, Egypt). Forty children with RhCh (mean age, 10.9 years) and 40 healthy controls were tested. An indirect-immunofluorescence technique was used for the detection of ANeurA. ANeurA were present in the sera of 100, 93, and 44% of the patients with acute, chronic, and past histories of RhCh, respectively. A definition of chronic chorea is presented for the first time. None of the control subjects had ANeurA in their sera. The presence of ANeurA correlated with disease activity. A statistically significant increase (P < 0.01) in the prevalence of ANeurA was found for patients with active chorea (acute and chronic) compared with the prevalence in patients with past histories of RhCh (controlled chorea). ANeurA were present in the sera of both patients with acute RhCh and patients with chronic RhCh, yet patients with acute RhCh showed more brightness and cell staining than chronic patients. The severity, number, and duration of each attack were not related to the presence of ANeurA. These results strengthen further the concept of autoimmunity being the basis for the pathogenesis of RhCh. The presence of ANeurA correlated with the activity of RhCh but not with the severity, number, or duration of attacks. Humoral immunity definitely plays a role in RhCh; thus, routine administration of corticosteroids to patients with acute RhCh is suggested to prevent neuron damage and chronicity. The chronicity of chorea is not due to a further increase in ANeurA but is probably due to sensitivity to these antibodies.