A child with a suspected genetic syndrome poses a challenge, especially when the child has cancer. Identifying an underlying genetic syndrome will likely have several tangible benefits for that child's care. Although individually rare, when taken as a group genetic syndromes are common enough that a pediatric oncologist likely follows several children with a genetic diagnosis, perhaps even unrecognized. Although there are a limited number of genetic syndromes that manifest an increased cancer risk, it is impossible for an oncologist to be able to recognize each one. For that reason, it is important to have some familiarity with the diagnostic approach to the child with a suspected genetic syndrome. This will facilitate identifying which children warrant further evaluation and testing by a medical genetics colleague. The genetics evaluation includes a detailed medical and family history and a physical examination that is focused on identifying minor anomalies and subtle dysmorphic physical differences. These are often overlooked by other healthcare specialists who are focused on the problem related to their area (e.g., the oncologist is focused on the child's cancer). However, for the geneticist, minor anomalies are the most valuable in diagnosing a dysmorphic genetic syndrome. Unfortunately, in many instances, even after a thorough evaluation and comprehensive genetic testing, a genetic syndrome diagnosis cannot be reached. In such cases the child should be reevaluated periodically, typically every 2-3 years, because new syndromes are regularly being identified, and genetic testing technologies are being improved on.