Objective: Group A Streptococcus has been associated with ADHD, tic disorders (TD), and obsessive–compulsive disorder (OCD) through anti-basal ganglia antibodies (ABGA). Method: We investigated the association between ABGA and streptococcal exposure with behavioral, motor, and cognitive measures in 38 children with ADHD not comorbid to OCD or TD (nc-ADHD) and in 38 healthy children. An additional group of 15 children with TD and/or OCD was examined. Results: ABGA titers were present in 3% of nc-ADHD patients and controls but in 27% of TD and/or OCD patients. Evidence of streptococcal exposure was similar between ADHD patients and controls living in the same urban area. Behavioral, motor, and cognitive measures were not associated with anti-streptococcal antibodies. Conclusion: ABGA do not distinguish nc-ADHD from controls. The differences in the frequency of streptococcal exposure in previous studies are determined by the dynamic nature of the infection rather than the behavioral phenotype of ADHD.