Structural equation modeling procedures are applied to the standardization sample of the Woodcock-Johnson III to simultaneously estimate the effects of a psychometric general factor (g), specific cognitive abilities, and reading skills on reading achievement. The results of this study indicate that g has a strong direct relationship with basic reading skills until about sixth grade. Also, g is found to have a strong indirect effect on reading fluency and comprehension across grade levels. Basic reading skills has a strong direct effect on reading fluency across grade levels. The effect of cognitive processing speed (Gs) on reading fluency increase with age. Reading fluency initially has a strong direct effect on reading comprehension, but this effect is reduced with age. Conversely, the direct effect of crystallized intelligence or knowledge (Gc) on reading comprehension increase with age. (Contains 2 figures and 4 tables.)