 This proposal is for an initial 6-month, single-arm, off label, open-label study with a 3 month extension phase offered to responders that will evaluate dose safety and efficacy of minocycline in 10 children, ages 3 to 12 years, with a primary diagnosis of autism and a history of developmental regression. The subjects will be evaluated by a diagnosticbehavioral assessment, and the extent of neuroinflammation judged by CSF cytokinechemokine profiles before and after the 6-month treatment. Subjects will also be given 0.6 mgkg vitamin B6 twice a day as a prophylactic for possible minocycline induced nausea and vomiting. If the results of this feasibility study are encouraging, we expect to conduct a double-blind, placebo-controlled trial of minocycline therapy. 