In this secondary analysis study, the authors explored the relations between reading comprehension and oral reading performance in fourth-grade students, using a data set from the U.S. National Assessment of Educational Progress (NAEP) special study of oral reading. The data set consisted of 1,713 students randomly selected from the 140,000 fourth graders who participated in the 2002 main NAEP reading assessment. Oral reading was measured by word-reading accuracy, rate, and prosody. The authors investigated how these variables related to NAEP comprehension across the ability distribution, with a focus on students with low comprehension scores. The results add to the literature in several ways. First, indicators of oral reading fluency continue to explain variation in reading comprehension, even when students had been given multiple opportunities to familiarize themselves with the passage that they read aloud. Second, word-reading accuracy and reading rate independently explained comprehension scores. Third, the authors observed qualitatively different profiles of fourth-grade readers with low comprehension scores. Nearly all students with reading rates lower than one standard deviation below the mean also had problems with word recognition, as evidenced by the relatively higher number of word-reading errors and low prosody ratings. The authors interpret these findings in light of the lexical quality hypothesis and the verbal efficiency theory, which emphasize the importance of word-level accuracy and automaticity to reading comprehension.