Twenty-one studies of the effectiveness of various grouping plans for elementary reading instruction are reviewed in this paper. Following the review, the studies are summarized according to the grade level with which they dealt, and conclusions are drawn regarding the most effective grouping plans. Among the conclusions reported are: (1) no one plan was effective for all elementary grades; (2) beginning reading instruction in the first and second grades was most effective in self-contained classrooms with a limited number of pupils; (3) sex grouping for reading favored boys in the first grade and was detrimental to girls; (4) in grades three and four, reading instruction in small, homogeneous groups was effective, although individualized instruction and heterogeneous grouping were found effective for fourth graders; and (5) in grades five and six, homogeneous grouping for high-ability students and heterogeneous grouping for average and below average students were favored. (GT)