English language learners (ELLs) represent one of the fastest growing student populations in the United States, and they experience reading difficulties and increased risk for Special Education identification compared to English-only speaking students (EOs). Lack of vocabulary knowledge is a contributing factor for reading difficulties. An immense gap in vocabulary knowledge exists between EOs and ELLs, making it difficult to directly teach the necessary amount of words to close this vocabulary knowledge gap. One promising approach to address this issue is to teach students to analyze words into their constituent morphemes (meaningful units of a word) in order to determine the meaning of words. If ELLs can be taught to use this strategy to derive meanings of unknown words while reading, they can take advantage of self-teaching opportunities to increase their vocabulary knowledge. This study investigated whether (a) ELLs at risk for reading difficulties could be taught a morphological analysis strategy to determine the meanings of words; (b) ELLs of differing reading profiles would respond similarly to the intervention; and (c) participants could generalize learning to novel words. Nine fourth and fifth grade ELLs with reading difficulties from a low socio-economic school participated in this study. The study employed a multiple baseline, single-case design. Visual analysis of the results established a functional relation between the intervention and an increase in students' vocabulary scores. In addition, the percentage of nonoverlapping data ranged from 90% to 100% for eight students. Moreover, students were able to generalize this learning to untaught words. These findings suggest that ELLs should receive targeted instruction in the morphological analysis to increase their vocabulary knowledge. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]