Sydenham's chorea (chorea minor, St. Vitus dance, rheumatic encephalitis), described by Thomas Sydenham in 1686, is considered one of the major manifestations of rheumatic fever (1, 2, 3, 4). Clinically it is characterized by involuntary movements, hypotonia, dysarthria, emotional disorders, and less frequently, by other neurological manifestations such as weakness, headache, seizures and sensory abnormalities (1,4). The motor disorders may be generalized or unilateral, in this case constituting a hemichorea (3). Chorea may present associated to other rheumatic fever manifestations during an acute episode, or in isolated form, characterizing the so-called "pure" chorea (5, 6, 7). Its etiology and pathophysiological mechanisms are still unclear, although its relation with a previous pathophysiological group A Beta-hemolytic streptococcus infection is well established (8). There is also evidence of the participation of immunological mechanisms in its pathogenesis, such as the finding of serum anti-nucleus caudatus and anti-subthalamic antibodies (9) and increase in IgG levels in cerebrospinal fluid of patients with chorea (10). In developed countries due to the reduction in rheumatic fever incidence and decrease in frequency of chorea as its manifestation (3, 11), the latter has become rare. However, in developing countries rheumatic fever remains a public health problem. In Brazil, in the last years an increase in the incidence of chorea has been observed as part of the clinical picture of rheumatic fever (12). The present study reports the clinical and laboratory findings of 187 cases of Sydenham's chorea followed-up during the period of January 1980 to December 1990 in two university centers in the city of Sao Paulo, Brazil.