There is now a sizable body of empirical research that reports moderate to strong relations between measures of oral vocabulary and reading comprehension. To further advance our understanding of how oral and written language acquisition intersect, this research examined the nature of this link between oral vocabulary and reading comprehension by more precisely defining, and measuring, theoretically derived facets of oral vocabulary. Different facets of the oral vocabulary system were defined and assessed separately based on models of the lexicon that distinguish between the number of lexical entries (vocabulary breadth), and the extent of semantic knowledge (vocabulary depth). Vocabulary depth was further expanded to include both measures of definitional knowledge and awareness of word associations; this latter measure was taken to reflect the organization of the lexical-semantic system. A total of 100 grade 6 students were tested on these facets of vocabulary, as well as on tests of phonemic awareness, word reading, and reading comprehension. Results revealed that reading comprehension was influenced directly by phonemic awareness, word reading, and vocabulary breadth. Reading comprehension was also influenced indirectly by lexical-semantic organization, which was found to predict unique variance in word reading. These results reflect the complexity of the relations between oral vocabulary and the comprehension of printed text, and highlight the relevance of measures of vocabulary breadth and depth in explaining individual differences in reading.