Background: Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcus (PANDAS) research is based on the hypothesis that infections trigger changes in behavior and movement in children. Methods: We enrolled 693 children (ages 3 to 12 years) into a systematic, longitudinal study. Data were collected monthly for 8 months (October-May) to determine point prevalence of Group A Streptococcal (GAS) infections, tics, behavior, and choreiform movements. Simultaneous throat cultures were obtained, and relational analyses were made between GAS and movement/observation ratings. Results: Combined behavior/GAS associations (concurrent with or 3 subsequent months to GAS) revealed a strong relationship, relative risk (RR) of 1.71 (p < .0001). Detailed analysis revealed that balance/swaying and non-tic grimacing were responsible for a significant proportion of this association (RR = 2.92, p < .0001). A strong seasonal pattern was found, with fall being more significant for GAS infections and observation ratings (p < .0001) compared with winter/spring. Children with repeated streptococcus (n = 64) showed higher rates of behavior and distal choreiform observations (p = .005). Conclusions: Motor/behavior changes were noted to occur in relationship to positive GAS culture with support that repeated GAS increases risk.