This study investigated the relationship between emotional responses and reading performance in middle-school students. Although a large number of prior studies have investigated the relationship between emotion and reading, those studies have concentrated primarily on relatively static and distal measures of emotion. In this research, we measured 7th- and 8th-grade students' (n = 44) emotional responses more proximally: during the reading tasks themselves. To do this, we used a cardiovascular indicator, respiratory sinus arrhythmia (RSA), that has been used frequently in psychophysiological studies of emotion but not, to our knowledge, in studies of reading. Results showed that the pattern of physiological response during reading predicted reading comprehension performance. Students with the most successful reading comprehension performance showed an initial orienting physiological response, followed by a lower threat physiological state when actually starting to read. Verbal retelling performance related strongly to emotional responses during reading, but multiple-choice performance was not related.