Behavioral side effects associated with benzodiazepines (such as clonazepam, diazepam, and lorazepam) are an easily overlooked and underrecognized problem with individuals who have mental retardation and can be inadvertently confused with other behavioral or psychiatric conditions. Based upon a literature review, behavioral side effects occurred for 13.0% of 446 individuals with mental retardation who were prescribed benzodiazepines for either behavioral or psychiatric conditions (n = 138, 17.4%), epilepsy (n = 208, 15.4%), or other medical conditions such as myoclonus or cerebral palsy (n = 100, 2.0%). Behavioral side effects for individual benzodiazepines for which data were available ranged from 11.4% to 25.0%. Implications of nonrecognition are discussed, and clinical indicators suggesting review by appropriate medical personnel are provided.