This publication reports statistics on persons with mental retardation and related conditions in state-operated residential facilities in the United States, based on a survey questionnaire completed by 50 states and the District of Columbia. Part 1 presents 12 tables that provide facility, population, and cost statistics for Fiscal Year 1990 that were compiled within state agencies. It includes statistics on small and large state-operated mental retardation facilities and facilities designated primarily for populations other than persons with mental retardation (in the vast majority of cases, psychiatric facilities). Part 2 places 1990 statistics within the longitudinal context of data gathered on state institution populations, resident movement, and costs of care since 1950. Part 3 includes a directory of public residential institutions (16 or more residents) for people with mental retardation/developmental disabilities. The directory lists facilities operating on December 31, 1990; those closed since 1960; and those projected to close by 1995. A list of 5 references and 28 data sources is included, along with state notes and notes concerning longitudinal data presentation. (JDD)