Sixty-six children from average and low-ability reading groups in grades one through five participated in a study of the effects of vocabulary instruction on reading comprehension. The children were pretested for their ability to identify words and to supply meanings for the new vocabulary words in the next basal reader story they encountered. The instructional conditions involved either a seven-step method of teaching new vocabulary in depth followed by a reading of the story, or merely a reading of the story without vocabulary instruction. Identical posttests followed each instructional condition. This procedure was repeated so that all the children participated in both instructional conditions. Results showed that vocabulary instruction did not produce significant gains on posttest performance in word identification. However, vocabulary instruction did significantly affect posttest scores for meaning knowledge. Beginning readers (grades one and two) showed significantly more gains overall than did intermediate-grade readers (grades three to five), while children in low-ability reading groups, especially, profited from direct word-meaning instruction. (RL)