The overall purpose of this study is to investigate lexical semantic representation in bilinguals who speak typologically different languages, specifically, Mandarin and English. Three questions are posed about semantic representation: 1) Do bilingual speakers demonstrate greater heterogeneity in semantic knowledge than monolingual speakers; 2) To what extent do bilingual speakers use paradigmatic and syntagmatic relations to organize their semantic knowledge; and 3) What is the cross- linguistic overlap in bilingual speakers' semantic representation. Thirty Mandarin- English bilingual adults and 30 monolingual English-speaking adults participated in a repeated word association task and generated three associations to each of 36 stimuli. The bilingual speakers completed the same task in their two languages on two different days whereas the monolingual speakers responded to the same 36 stimuli on two different days. Results indicated that 1) the bilingual speakers produced a more heterogeneous set of responses in English than monolingual speakers; heterogeneity was greater in English than Mandarin among the bilingual speakers; 2) the bilingual speakers produced more paradigmatic associations (e.g., happy-sad, spoon-chopsticks, catch-throw) and fewer syntagmatic associations (e.g., happy-smile, spoon-eat, catch-ball) than the monolingual speakers; and 3) approximately 48% of the bilingual speakers' responses were cross- linguistic synonyms, whereas approximately 76% of the monolingual speakers' responses were identical from session 1 to session 2. These findings suggest that late bilinguals (second language learners) use categorical relations to organize their semantic knowledge to a greater extent than monolingual speakers and that reduced experience with a second language can lead to greater heterogeneity in semantic knowledge in that language. The findings also suggest that bilingual speakers have more distributed semantic representations than monolingual speakers. Additional research is needed to explore the areas of heterogeneity, categorical organization, and cross-linguistic overlap in order to further our understanding of bilingual speakers' semantic knowledge representation. / text