This study examined the degree to which parents are informed about syndrome-based behaviors in children with three genetic mental retardation syndromes: Down syndrome (n = 21), Prader-Willi syndrome (n = 25), and Williams syndrome (n = 21). Parents were informed regarding blatant behavioral features associated with their children's syndromes (especially concerning maladaptive behaviors) but were less informed about certain subtle syndrome-based cognitive processing outcomes. Compared to the parents of children with the other two syndromes, parents of children with Down syndrome were more informed about syndrome-related behaviors; in addition, greater numbers of individuals (e.g., parents, school psychologists, teachers, speech—language pathologists) brought information about children with Down syndrome into the classroom setting. Across all three groups, the supportive educational services received by the children were generally not adjusted to syndrome profiles.