This paper explores what is meant by "thinking" in a target language. Factors that determine both unplanned and planned use of more than one language for thinking are discussed, and empirical data from a mini-survey and from personal language learning and language using experiences are presented. The role of target-language thinking in improving language ability is reviewed, also from empirical data from the survey and personal experiences. Mental translation in the reading of intermediate college French, the language of thought in an elementary school Spanish immersion program and thought patterns in the production of speech acts by college English as a Foreign Language (EFL) students are also examined. It is concluded that there are definite benefits from making an effort to think in the target language. Actual examples from multilingual subjects are given, and the mini-survey is appended. (Contains 36 references.) (Author/NAV)