Recent advances in genetics have yielded important insights into the etiology of autism spectrum disorder (ASD) and other neurodevelopmental disorders (NDDs). Professional societies such as the American Academy of Pediatrics and the American College of Medical Genetics and Genomics now recommend testing patients newly diagnosed with ASD and some other NDDs with chromosomal microarray analysis (CMA). CMA can identify alterations in the number of copies of various regions in the entire genome for the purposes of comparison with known normal and pathogenic patterns.