This manuscript describes an instructional strategy, system of least prompts, and reviews the use of the procedure in the applied research literature. The literature is analyzed in terms of the populations for which the procedure has been used, the type of skills that have been taught with the procedure, and the results when the procedure was employed. The literature also is described in terms of previously identified parameters of the system of least prompts including (a) the number and type of prompts included in the least-to-most assistance prompt hierarchies, (b) the presentation of the target stimulus at each prompt level, (c) use of a fixed response interval, and (d) the delivery of reinforcement following correct prompted and unprompted responses. Summary statements and recommendations about future use and research are included.

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Systematic intructional strategies that investigators have used with students who display moderate to severe handicaps were identified and defined. The investigations which directly compared two or more strategies were analyzed, and summary statements/recommendations about the relative effectiveness and efficiency of the strategies were made. Analyzing the effectiveness of the procedures involved determining which strategies successfully taught skills to subjects. The efficiency of the strategies was analyzed on measures which indicated the skills were taught in a productive and timely manner (i.e., trials to criterion, sessions to criterion, errors to criterion, direct instruction time). Recommendations for future research and practice include (a) conduct more studies comparing the effectiveness and efficiency of instructional strategies, (b) conduct investigations of the specific variables of single strategies to identify the most efficient use of each procedure, (c) expand the efficiency measures to assess whether students learn information not directly targeted for instruction, and (d) conduct research to determine which strategy is best to use with given types of students and skills.

A progressive time delay procedure in one-to-one instructional sessions using massed-trial presentation was compared to transition-based teaching that involved distributed trials presented during transitions from one activity to another. Four preschool children with developmental delays were taught to read words and name letters/numerals and to produce manual signs for photographs. The classroom teacher conducted one daily massed-trial session with each student using progressive time delay for a set of behaviors, and provided an equal number ofdbtributed trials at transition times to each student with a transition-based teaching procedure for another set of behaviors. The procedures were compared on the number of children meeting criterion (effectiveness) and on the number of trials and errors to criterion and the percentage of errors to criterion (efficiency). The parallel treatments design was used to evaluate the two instructional strategies. The results indicated that (a) both procedures were implemented reliably, (b) both procedures were effective in establishing criterion level performance, and (c) no substantial differences existed on the efficiency measures, although the number and percentage of errors were slightly higher for 3 of the 4 children with the transition-based teaching procedure. Implications for practice and future research are described.Teachers must make numerous decisions in planning and implementing appropriate early education experiences for young children with developmental delays and disabilities. Among others, they must select appropriate instructional strategies and plan times for using those 1 Currently with the Department of Special Education, University of Georgia, Athens, GA. , 1992). When selecting instructional strategies, teachers may choose from several potential procedures that have been found effective in establishing acquisition of new behaviors; these include progressive time delay, constant time delay, mostto-least prompting (decreasing assistance), the system of least prompts (increasing assistance), and others (Demchak, 1990; Wolery, procedures (Bailey & Wolery