 Children ages 3 to 12 with regressive autism may be eligible for this study. The children will take minocycline and vitamin B6 daily for 6 months. Prior to starting the medication and vitamin B6, children will receive a comprehensive diagnostic assessment for autism as well as a physical examination, medical history, and laboratory tests. Children will then receive ongoing assessments to monitor their behavior, communication, language skills, and medical issues at 2 weeks, and at 1, 2, 4, 6, and 12 months. Children who respond to the treatment will receive an additional 3 months of minocycline and vitamin B6. 