There is a multitude of research on vocabulary methods or strategies, how many relate to second language learners and the importance of vocabulary knowledge to reading comprehension. Researchers have explored the possibility that grouping words in a manner other than the traditional list of nouns, all fitting under a common theme, might be more beneficial for students. This suggests that it might be helpful to give a list of words that are not semantically related. However, there is a deficit in the research on teaching vocabulary by using different word clusters for elementary students and for students learning a second language. The study presented here attempted to answer the question "Will grouping vocabulary words thematically result in more words learned by second language students than semantic grouping?" In addition, this research produced data on the retention of new vocabulary data over 3 weeks and the students' opinions about the two types of word clusters. Participants were third, fourth, and fifth grade students receiving the same level of English-as-a-Second-Language (ESL) instruction. Results showed both word groupings were beneficial, suggesting teachers might consider using both semantic and thematic groupings to help second language elementary students learn new vocabulary words. Twenty-three appendices (containing sample worksheets, questionnaires, letters, lists, and other items associated with the research) and 22 references are included. (Author/KFT)