The purpose of this longitudinal study was to explore the impact of a direct reading instruction program, "Reading Mastery (RM)," on literacy performance of students over a five-year period. Initially, 700 students in grades K-3 were randomly selected from six elementary schools to participate in the study; an additional 100 randomly-selected kindergarten students were added to the sample for each subsequent year of the study. Literacy performance was assessed using oral and silent reading performance measures from the "Qualitative Reading Inventory-3 (QRI)," reading scale scores from the "Mississippi Curriculum Test (MCT)," and cloze scores from the "Hunter & Grundin Literacy Profiles (HGLP)." Because all students in the school system were receiving "RM" no comparison group was available to aid interpretation of the findings. In an attempt to overcome this difficulty, data were analyzed in three parts. First, only data for students who began "RM" in kindergarten were examined descriptively and graphically. Second, statistical comparisons by grade level were made between students who began "RM" in kindergarten and those who began "RM" in a later grade. Third, descriptive and graphical comparisons of group performance overtime were made between groups of students who began "RM" at different grade levels. Although a few statistically significant differences were found between students who began receiving "RM" instruction in kindergarten and those who began receiving "RM" at a later grade, the preponderance of data provided little evidence to support the viability of "RM" for improving reading comprehension. (Contains 20 tables and 45 figures.)