Thiol-modulating mechanisms affecting the cytotoxicity of Thimerosal (TM) have been identified. Importantly, the emergence of Autism Spectrum Disorder (ASD) symptoms post-6 months of age temporally follows the administration of many childhood vaccines. The purpose of the present critical review is provide mechanistic insight regarding how limited thiol availability, abnormal sulfation chemistry, and decreased GSH reserve capacity in children with an ASD could make them more susceptible to the toxic effects of TM routinely administered as part of mandated childhood immunization schedules.