Abstract: Different models of bilingualism and concept acquisition offer varying theoretical viewpoints from which to understand and to investigate the manner in which memory traces are encoded, stored, and retrieved. Experiment 1 established that French-English bilinguals tended to retrieve memories of events that were experienced in the same language that was being used in performing the task. This finding supported proposals that memory representations are encoded and stored as linguistic traces rather than as abstract nonlinguistic traces. In Experiment 2, however, Spanish-English bilinguals demonstrated no preference in retrieving memories of events that had been experienced in the language of retrieval. Nor did the bilinguals demonstrate any preference in mentally remembering the events in the same language in which they had experienced the event under a strict criterion. Because the bilinguals who had participated in Experiments 1 and 2 represented two different types of bilinguals in terms of their history of acquisition of the second language, Experiment 3 examined language preference in a situation where subjects were free to choose the language in which they completed the memory task. This study replicated the findings of Experiment 1 in demonstrating a language preference in remembering events in the same language in which they had experienced the event. The contradictory results of Experiment 2 and 3 were resolved in terms of the history of language use by the Spanish-English bilinguals. In comparison to the French-English bilinguals, Spanish-English bilinguals tended to interact in more bilingual environments, which contributed to their ease in describing events in either language. Experiment 4 revealed that contrary to popular belief, autobiographical memories related in a different language than that in which the events had been experienced did not contain fewer overall details. Those autobiographical memories had comparable levels of detail; however, the emotional content was judged both by the narrators and by independent raters to be less expressive. The results of these four experiments revealed that language plays an influential role in the encoding, retrieval, and expression of autobiographical memories.