In defining the focus of this review, the authors note that the term "mental retardation" only includes those persons with both mental and adaptive deficiencies. The limited number of investigations of the maltreatment of mentally retarded children is verified. The studies agree on the special conditions of vulnerability of the retarded child, due both to intrinsic requirements and characteristics as well as the perceptions and experience of those interacting with the victim. Although determining a prevalence rate for the maltreatment of this population is difficult, estimates exceed rates for the nondisabled population, with percentages between 5 percent and 7 percent. Problems in the lack of data uniformity and accuracy are due to the lack of data in many reports, variations in the definitions of child maltreatment, and the fact that the number of cases reported is a fraction of the real number. Most studies have focused on child maltreatment, on sexual abuse, and on the family as the context for maltreatment. Some authors, however, have addressed the institutional abuse of the mentally retarded. The need for complementary studies as well as prevention and intervention measures is needed, both in the family and in institutions. The first step is to generate awareness of the problem in direct-care professionals. 165 references