 This study is a clinical trial of oral sulforaphane as broccoli seed powder in 50 boys and girls 3-12 years with ASD in 3 phases over 36 weeks. In Phase 1, 25 children will receive active drug and 25 will receive placebo for 15 weeks; in Phase 2, all children will receive sulforaphane from 15-30 weeks; in Phase 3, children will receive no treatment for 6 weeks. Study visits will take place at screening, 7, 15, 22, 30 and 36 weeks, when the Ohio Autism Clinical Clinical Impressions Scale - Severity and Improvement OACIS-S and OACIS-I, Aberrant Behavior Checklist ABC and Social Responsiveness Scale SRS will be recorded. Children will be monitored with physical examinations and for toxicity with clinical laboratory studies and examine possible biomarkers: Nuclear factor-erythroid factor 2 Nrf2, oxidative stress and mitochondrial function, the mechanistic target of rapamycin mTOR pathway and cytokine expression. In addition, prior to the main clinical trial, a pilot study will be carried out in 10 children with ASD, 6-12 years of age, who will receive sulforaphane, 2.2 micromoleskg daily for 14 days. Blood and urine samples before and at the end of treatment will be collected, in order to measure several parameters that are likely to demonstrate expected effects of sulforaphane, to standardize the assays and procedures, and to determine the most effective measures. 