Antistreptolysin O (ASO), anti-desoxyribonuclease B (anti-DNAse B), and anti-nicotinamide adenine dinucleotidase (anti-NADase) titers were determined on patients with Sydenham's chorea and a matched group of controls. For each of the antibodies studied, elevated titers were found in a significant percentage of patients with chorea as compared with control individuals. This finding was also true of patients with "pure chorea" on whom antibody titers were performed within 6 months of the onset of choreic symptoms. Ten of 30 such patients failed to show an elevated ASO titer. Four of these were found to have markedly elevated anti-DNAse B titers. Elevation of two or more antibody tests, which is highly suggestive of recent streptococcal infection, was found in the majority (63%) of patients with pure chorea seen within 6 months as compared with the control group (10%). The practical and potential usefulness of multiple streptococcal antibody tests in patients with pure Sydenham's chorea is discussed.