This study examines the relationship between ESL learners' depth of vocabulary knowledge, their lexical inferencing strategy use, and their success in deriving word meaning from context. Participants read a passage containing 10 unknown words and attempted to derive the meanings of the unknown words from context. Introspective think-aloud protocols were used to discover the degree and types of inferencing strategies learners used. The Word-Associate Test (WAT) (Read, 1993) was used to measure the learner's depth of vocabulary knowledge. Results indicate a significant relationship between depth of vocabulary knowledge and the degree and type of strategy use and success. They reveal that (a) those who had stronger depth of vocabulary knowledge used certain strategies more frequently than those who had weaker depth of vocabulary knowledge; (b) the stronger students made more effective use of certain types of lexical inferencing strategies than their weaker counterparts; and (c) depth of vocabulary knowledge made a significant contribution to inferential success over and above the contribution made by the learner's degree of strategy use. These findings provide empirical support for the centrality of depth of vocabulary knowledge in lexical inferencing and the hypothesis that lexical inferencing is a meaning construction process that is significantly influenced by the richness of the learner's pre-existing semantic system.