We will recruit 50 children with DSM-IV ASD (autistic disorder and Asperger's disorder) aged 3-15, their siblings, and 50 age-, sex-, and handedness-matached healthy controls. A number of instruments will be used to measure autistic symptoms, functional levels, and cognitive ability (i.e. ADI-R, ADOS, SCQ, SRS, and CAST; WISC-III (WPPSI-R, Bayley), DDST, CPM, and SPM; CPT, WCST, Cambridge Neuropsychological Test Automated Batteries). We will also look directly at the brain for structural and functional connectivity using the DSI and fMRI, respectively. We will repeat the assessments at a 2-year interval. The major tasks consisted of five parts: (1) 3 months—recruitment of subjects, researcher training, and pilot study; (2) 1 years 6 months—clinical, neuropsychological, genetic, DSI and fMRI assessments of 150 subjects; (3) 6 months—data analysis, reports to subjects, and manuscript preparation; (4) 1 years 6 months—same assessment of 150 subjects at a 2-year interval; (5) 4 months—data analysis, reports to subjects, and manuscript preparation.