This study is designed to test the effectiveness of the antibiotic Amoxicillin for the treatment of Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS). Patients will receive Amoxicillin for six weeks and placebos "inactive sugar pills" for six weeks in order to see if the medication is truly working. Effectiveness of the treatment will be based on the presence or absence of symptoms. If at the end of the study Amoxicillin is proven to be effective treatment for PANDAS patients may be offered the opportunity to continue taking the medication for an additional six months.