This clinical review is designed to assist the pediatrician, family physician or internist in caring for the child, adolescent, adult and family in whom a diagnosis of 16p11.2 deletion syndrome has been confirmed by chromosome analysis. Although a pediatrician's initial contact with the child is usually within the first 5 years of life, occasionally an adolescent or adult will be tested and diagnosed after their sibling or child has been diagnosed with the same condition. Age specific guidance for the clinician is provided in Supplement Fig 1. 16p11.2 deletion is the most common genetic cause of neurodevelopmental disorders (1) and autism spectrum disorder (ASD) and is characterized by motor speech disorder, language disorder, motor coordination difficulties, some degree of developmental delay, below average cognition, learning disabilities in both verbal and nonverbal domains and psychiatric conditions. (Table 1) (2). While those with 16p11.2 deletion have some degree of development delay, the severity can vary significantly. Awareness and prompt attention to the issues is important in optimizing lifelong outcomes. There are no pathognomonic phenotypic features that can facilitate rapid clinical diagnosis, however, vertebral anomalies (often leading to scoliosis) (3), hearing impairment, cardiac malformations (3), congenital anomalies of the kidneys and urinary tract (4), slightly below average height (3), macrocephaly (3), and craniosynostosis (3) are noted in some individuals with the deletion. No patient will have all of these features.