To promote the deinstitutionalization of mentally retarded individuals, a three-phase assessment prescription system has been developed. It conceptualizes return to the community as a series of transfers from a restrictive non-programmatic environment (phase one) through specialized short-term program-oriented rehabilitation (phase 2) to the least restrictive living alternative possible (phase 3). The Post Entry Instrument provides a detailed observation-based assessment device for measuring behavioral change and progress during phase two. It has two forms: preschool (birth-through eight years), and adolescent/adult (ages eight through late middle age). Both forms consists of five subscales: motor development, self-help, academic/cognitive, language, and socialization. Each subscale contains a hierarchy of five levels, the lowest representing characteristic behaviors of a minimally functioning individual, and the highest describing independently functioning individuals. Each item appears as a behavioral objective. Scoring depends upon the level at which the individual performs a given item: self-initiated, with verbal, modeling or physical cue; or making no response. Both forms of the Post Entry Instrument are included, along with directions for administering and scoring. (Author/CP)