Comprehension is the reason for reading, and vocabulary plays a significant role in comprehension. The question is, What kind of instruction best promotes the development of comprehension and vocabulary? The National Reading Panel (National Institute of Child Health and Human Development, 2000) concluded that there are eight effective or promising strategies for teaching reading: comprehension monitoring, cooperative learning, graphic and semantic organizers, story structure, question answering, question generation, summarization, and multiple-strategy use. The final strategy is the basis for the five-week study reported in this article. The purpose of the study was to determine the effectiveness of systematic direct instruction of multiple metacognitive strategies designed to assist students in comprehending text. Specifically, the reading comprehension and vocabulary achievement of 119 third-grade students was investigated to determine whether instruction that incorporated metacognitive strategies led to an increase in the reading comprehension of expository text. In addition, the investigation was also designed to determine the impact of the metacognitive strategies on vocabulary. This research project took place in six third-grade classrooms in two urban elementary schools in the southwest United States that were deemed demographically and academically equal. One school was selected as the intervention school and the other school was the comparison school. The students in both schools were pretested before the five-week study and posttested at the end of the study. Results indicated that the metacognitive reading comprehension instruction significantly improved the academic achievement of third-grade students in the domains of reading comprehension and vocabulary over the other instruction that was offered to the students in the comparison school. The intensity of the study and the systematic instruction of metacognitive strategies led to positive effects for understanding written text, which is the reason for reading. (Contains 3 figures and 1 table.)