The investigators propose a pilot, single blind, placebo run-in, dose finding study of pioglitazone in children with autism with the ultimate goal of identifying appropriate dosing and outcome measures for a larger follow-up randomized placebo controlled clinical trial. The specific aims of this study are: 1) To examine the safety of pioglitazone in children with autism spectrum disorders (ASD) ages 5-12 years; 2) To identify appropriate outcome measures to be used in a follow-up multisite randomized control trial of pioglitazone in children with ASD; 3) To determine the maximum tolerated dose to be used in the follow-up multisite randomized controlled trial; 4) To examine the effect of pioglitazone on markers of inflammation (cytokine levels) and oxidative stress (superoxide dismutase, malonyl aldehydes); 5) To explore the relationship between different doses and response to treatment.