We analyzed the clinical, radiologic, and immunologic characteristics of 50 patients with chorea and the antiphospholipid syndrome (APS) (6 from our clinics and 44 from a MEDLINE computer-assisted review of the literature from 1985 through 1995). Forty-eight (96%) patients were female and 2 (4%) were male. Twenty-nine (58%) patients had defined systemic lupus erythematosus (SLE), 6 (12%) had "lupus-like" syndrome, and 15 (30%) patients had "primary" APS. Mean age of patients in this series was 23 +/- 12 years (range, 6-77 yr); mean age at presentation of chorea was 21 +/- 12 years (range, 6-77 yr). In 11 (22%) patients, the onset of chorea was in childhood (6-14 yr), and in 2 (4%) patients it presented at 60 years or more. Six (12%) patients developed chorea soon after they started taking estrogen-containing oral contraceptives, 3 (6%) developed chorea gravidarum, and 1 (2%) patient developed chorea shortly after delivery. Most patients (66%) presented only 1 episode of chorea. Chorea was bilateral in 55% of patients. Computed tomography and magnetic resonance imaging scans reported cerebral infarcts in 35% of patients. The following antibodies were detected: lupus anticoagulant (92%), anticardiolipin antibodies (91%), antinuclear antibodies (82%), anti-DNA (59%), anti-Ro (10%), anti-RNP (8%), anti-La (2%), and anti-Sm (2%). The chorea in these patients responded to a variety of medications, for example, steroids, haloperidol, antiaggregants, anticoagulants, or a combination of therapy, usually prescribed in the presence of other manifestations of APS or SLE. However, many patients responded well to haloperidol and to the discontinuation of oral contraceptives if this was the precipitating factor.