This article reports the behavioral, biochemical, and electrophysiological effects of four therapeutic crossed-sequential double-blind trials with 60 autistic children: Trial A--vitamin B6 plus magnesium/magnesium; Trial B--vitamin B6 plus magnesium; Trial C--magnesium; and Trial D--vitamin B6. Therapeutic effects were controlled using behavior rating scales, urinary excretion of homovanillic acid (HVA), and evoked potential (EP) recordings. The behavioral improvement observed with the combination vitamin B6-magnesium was associated with significant modifications of both biochemical and electrophysiological parameters: the urinary HVA excretion decreased, and EP amplitude and morphology seemed to be normalized. These changes were not observed when either vitamin B6 or magnesium was administered alone.