This research studied whether deaf students' component reading processes may interact with other in a competitive manner. Vocabulary and syntax, two processes known to directly and adversely affect the comprehension of many deaf readers, were studied to determine if they may influence each other, affecting the contribution that each one makes separately to reading comprehension. Multiple regression analyses were conducted on predictor variables that included measures of vocabulary and syntactic competence, as well as a variable summarizing the interaction of vocabulary and syntax. The criterion variable was a composite of comprehension performance on a cloze procedure and on a more traditional reading test. Results were cross-validated by separate regressions on data samples from three populations of profoundly deaf readers: 100 adolescents from oral school programs, 113 adolescents from total communication programs, and 211 students entering a postsecondary institution that used total communication. In each regression, the Vocabulary × Syntax interaction variable emerged as the most critical of the three predictors. Further analyses of the interaction revealed that among subjects in the highest quartile of syntactic competence, the correlation between vocabulary competence and reading was significantly greater than it was in the lower three syntax quartiles. In contrast, the relationship between syntax and comprehension remained stable across all four quartiles of vocabulary competence. This suggests that unless deaf readers have achieved a reasonable level of syntactic competence it may be difficult for them to capitalize fully on their vocabulary knowledge. The finding that limitations in one reading process can interfere with the application of another is consistent with the theory of Capacity Constrained Comprehension of M. Just and P. Carpenter (1992). Because syntax can exert both a direct and an indirect influence on comprehension, it should be an important focus in instructional programs.