Discussion and research concerning class size can be traced back at least to the 12th century. An overview of recent research on the subject is provided in this report. The paper, which serves as an introduction to a symposium on class size, examines research that has appeared in the past 20 years, but it concentrates on the results of a longitudinal study--Project STAR (Student Teacher Achievement Ratio)--that was considered a controlled experiment for class size research. The results of STAR and other similar programs show that students do benefit from smaller class sizes, and these results are reinforced by any study that finds a positive relationship between tutoring and achievement, cooperative learning and positive results, and other programs that emphasize small-group learning. Critics have claimed that the studies are in error or that, even if effective, such programs are much too expensive to implement. But, it is countered, research has not shown the harmful effects of small classes or that larger classes are better for children. It is hoped that the research on class size will influence educators and policy makers to move forward on this issue. (Contains approximately 125 references.) (RJM)