Demographic and background characteristics, pre-adoption motivation, and post-adoptive adjustment of 20 British families who had, among them, adopted 23 mentally retarded children were explored through semi-structured interviews and questionnaires. Children in the sample had been in their adoptive homes an average of 17 months; 48% were under 5 years old. Twenty mothers were interviewed in their homes, either alone or with the father; data from mothers alone was reported. A 10-item mutiple-choice questionnaire assessed family functioning following placement. A 285-item true-false Questionnaire on Resources and Stress (Holroyd) was subsequently completed and returned by all families. General characteristics of the sample indicated that adopters of mentally retarded children are familiar with the handicap, are likely to be of middle-class background, and adopt for a variety of reasons, including biological infertility, religious conviction, and personal/professional experience with the handicap. Among suggested conclusions was that adoptive families may experience less stressful adjustment than biological families of retarded children. (The literature on families who adopt mentally retarded children, as well as on family reactions to biologically borne handicapped children, is reviewed.) (JW)