This executive summary reports on a study which utilized meta-analysis and best-evidence synthesis techniques to evaluate 13 research studies on the academic, social, and psychological effects upon learners who are gifted and talented of three grouping practices: (1) ability grouping for enrichment; (2) mixed ability cooperative grouping for regular instruction; and (3) grouping for acceleration. It was concluded that the research showed strong, consistent support for the academic effects of most forms of ability grouping for enrichment and acceleration, but that the research is scant and weak concerning the socialization and psychological adjustment effects of these practices. Claims for the academic superiority of mixed ability grouping or for whole group instructional practices were not substantiated for gifted and talented learners. Guidelines are offered suggesting that: students who are gifted and talented should spend most of their school day with others of similar abilities and interests; cluster grouping of gifted students within an otherwise heterogeneously grouped classroom can be considered when a full time gifted program is not feasible; a cross-grade grouping option could be offered in the absence of a full time gifted program enrollment; gifted and talented students should be offered a variety of acceleration and enrichment based options; and mixed ability cooperative learning should be used sparingly for students who are gifted and talented. (15 references) (Author/DB)