This study was designed to investigate the effects of discovery and expository methods of presentation on the immediate acquisition and retention of geometry concepts by seventh graders. Four geometry concepts, "quadrilateral,""rhombus,""trapezoid," and "parallelogram," were presented in written lessons which used either an expository or a discovery approach. Ss studied the lessons on four consecutive days. They were given a test on the concepts either immediately after completion of the lessons or one day or 21 days after completion of the lessons. Ss who received the test one day after completion were retested 21 days after completion. The findings of the study were as follows: (1) Ss who studied the expository lessons had significantly higher scores than Ss who studied the discovery lessons; (2) An independent groups analysis revealed no significant difference between treatment groups. However, a repeated measures analysis revealed that Ss in the discovery group tended to forget less than Ss in the expository group over the 21-day retention interval; and (3) The expository group spent only one-third as much time on the lessons, yet had immediate acquisition superior to the discovery group and 21-day retention equal to the discovery group. (Author/JM)