This review of the literature summarizes findings on instructional grouping issues and academic achievement of gifted elementary students. The review addresses problems of using standardized tests to evaluate instructional effectiveness of grouping arrangements, distinctions between providing the same curriculum and a differentiated curriculum to gifted groups, and grouping within the heterogeneous class or in self-contained classes. It is concluded that research evidence strongly supports grouping of students by ability for at least the curriculum areas of reading and mathematics. In addition, there is also evidence that once students are grouped by ability, the level of instruction and pace of learning must be adapted in order to gain the maximum benefit for the student. (20 references) (DB)