Oral language and word reading skills have important effects on reading comprehension. The Wechsler Individual Achievement Test-Third Edition (WIAT-III) measures both skill sets, but little is known about their specific effects on reading comprehension within this battery. Path analysis was used to evaluate the collective effects of reading and oral language measures on reading comprehension in a total of 456 students referred for special education evaluations. Students were split randomly into two groups (calibration and validation) for model construction and testing. Results indicate that these measures demonstrate a number of effects on reading measures that go beyond the expressive/receptive distinction in the test manual and add to the validity evidence for the WIAT-III. Implications for practice and study limitations are discussed.