Mercury has been investigated as a possible cause of autism, but its association with autism remains uncertain. Hertz-Picciotto et al. examined blood Hg levels and sources of Hg exposure among participants in the Childhood Autism Risk from Genetics and the Environment (CHARGE) Study, including 2- to 5-year-old children classified as having autism or an autism spectrum disorder (autism/ASD, n = 249), developmental delay (DD, n = 60), and typical development (TD population-based controls, n = 143) based on standardized criteria and clinical examination. Information on household, medical, and dietary exposures was provided by mothers, and blood Hg was measured by inductively coupled plasma mass spectrometry. Fish consumption strongly predicted blood Hg, and lower average blood Hg levels observed in the autism/ASD group were consistent with lower levels of fish consumption in autism/ASD children compared with TD controls.