Reading comprehension scores from the Wechsler Individual Achievement Tests, the Gates-MacGinitie Reading Test, and the Gray Oral Reading Test were examined in relation to measures of reading, language, and other cognitive skills that have been hypothesized to contribute to comprehension and account for comprehension differences. In a sample of 97 first through tenth graders, the relative contributions of word recognition/decoding and oral language skills to comprehension varied from test to test. The inclusion of reading speed accounted for additional variance, but prediction of comprehension scores was minimally improved by including measures of rapid serial naming, verbal memory, IQ, or attention. The findings suggest that commonly used tests of reading comprehension, such as the three we compared, may not tap the same array of cognitive processes. Implications for research and practice are discussed.