BACKGROUND Various investigations have revealed that the promotion of cognitive and metacognitive strategies can improve reading comprehension and that when readers receive this type of instruction, they can use monitoring processes and regulation strategies adequately. The goal of this work is to analyze the effects of strategic and metacognitive instruction on reading comprehension processes and strategies, using the "Aprender a Comprender" [Learning to Understand] program. METHODS Instruction was carried out in the classroom by two teachers during six months. Ninety-four students participated, 49 from 5th grade and 45 from 6th grade. A pretest-intervention-posttest-follow-up design was used with a comparison group by grade. RESULTS The analysis of variance shows an impact of the intervention and its differential maintenance in each grade. The 5th-grade intervention group scored higher than the comparison group in the reading comprehension test, both at posttest and at follow-up. The 6th-grade intervention group scored higher than the comparison group in the Planning scale, both at posttest and at follow-up. CONCLUSIONS Textual strategy instruction favors reading comprehension and the progressive development of planning, which is necessary for supervision and regulation, and its effects are maintained over time.