The causes of high and low reading achievement were investigated using a causal model that involves 4 echelons of proximal and distal causes. In Study 1, 55 elementary students were individually administered a battery of tests in 2 sessions-around 2 hr each session on Saturdays. In Study 2, 83 students in Grades 4 and 5 were tested in their classrooms. There were 1 or more tests that were designed to measure almost all of the constructs in the causal model, plus 2 tests from the Woodcock Reading Mastery Tests (Woodcock, 1973) and the Reading Comprehension test from the Iowa Tests of Basic Skills (H. D. Hoover, Hieronymus, Frisbie, & Dunbar, 1993). The results generally were consistent with the causal model because (a) the fit of structural equations to the first 3 echelons of the model was. 89 or higher in 8 analyses, and (b) when the best measures of each construct were used, the normed-fit-index (Bentler & Bonett, 1980) was. 98 in Study 1 and. 95 in Study 2. There was considerable correlational support for the first 3 echelons of the causal model of reading achievement, that is (a) the 2 proximal causes of reading achievement are reading level and rate level, (b) the 2 proximal causes of reading level are verbal knowledge level and word identification knowledge level, and (c) the 2 proximal causes of rate level are word identification knowledge level and naming speed level. However, the 2 measures that were developed to measure verbal aptitude and pronunciation aptitude, at Echelon 4 of the model, were not highly consistent with the hypothesized causal connections. An implication of the model is that teaching and learning relevant to improving listening comprehension (meaning emphasis) and word identification (code emphasis) proximally affect verbal knowledge and pronunciation knowledge, and distally affect reading level, reading rate, and reading achievement.