Linguistic computing can make two important contributions to second language (L2) reading instruction. One is to resolve longstanding research issues that are based on an insufficiency of data for the researcher, and the other is to resolve related pedagogical problems based on insufficiency of input for the learner. The research section of the paper addresses the question of whether reading alone can give learners enough vocabulary to read. When the computer's ability to process large amounts of both learner and linguistic data is applied to this question, it becomes clear that, for the vast majority of L2 learners, free or wide reading alone is not a sufficient source of vocabulary knowledge for reading. But computer processing also points to solutions to this problem. Through its ability to reorganize and link documents, the networked computer can increase the supply of vocabulary input that is available to the learner. The development section of the paper elaborates a principled role for computing in L2 reading pedagogy, with examples, in two broad areas, computer-based text design and computational enrichment of undesigned texts. (Contains 15 figures, 3 tables and 7 notes.)