Expressed emotion (EE) is a measure of the affective relationship between two people characterized by criticism, hostility, and emotionally over-involved attitudes. Outside of the field of intellectual disabilities, there has been considerable interest in EE as an environmental marker that explains variance in the severity and/or course of a number of psychiatric disorders. Researchers have also studied EE in parents and found strong associations with children's behavior problems. In this review, we focus on the data from 11 published studies of EE in families of children and adults with intellectual disabilities. We conclude that there is evidence for the presence of high EE in some families, and that this alone should concern researchers and clinicians and set an agenda for considerable future research effort. We also note a lack of attention to the measurement of EE in intellectual disability. In terms of the existing evidence base, we suggest that there is support for the hypothesis that behavior problems in children and adults with intellectual disabilities may be related to high EE in parents, and a small amount of data predicting over time support the putative causal effect of high EE on maintaining or exacerbating behavior problems. Given that EE is perhaps best conceptualized as the result of an interaction between caregivers and those cared for, there is a need to explore interventions that may help to remediate high EE within families. It is also important to understand from this position that EE may be a normative part of the experience of caring for someone under very stressful circumstances and not something for which families are blamed. Other future research priorities and some implications for practice are also discussed.