The nine major empirical studies of "Lexical Issues in Language Learning" address key issues in the development and use of vocabulary by child bilinguals and older second language learners. The thematic focus in this collection of "Language Learning" articles is on the assessment of lexical development in bilinguals at different points in the lifespan; the psycholinguistic factors that determine the learnability of second language lexis; and the conditions on communication tasks that promote the learning and retention of second language vocabulary or lead to different strategies for handling lexical problems. The introductory chapter presents an overview of current trends in lexical research in second language learning, and assesses the contribution of each of the nine studies to knowledge in the field. The chapters are organized in three sections in accordance with the main themes of the volume. The preface to each individual article contains a brief update assessing the contribution of the research in question to the current knowledge about second language lexical acquisition. The studies address learning in diverse situations internationally, utitlize innovative research methods conducted with the highest levels of expertise, and concern acquisition in various languages: Chinese, English, French, German, and Spanish. The volume is not only a valuable reference tool for researchers and scholars active in this field, but also form excellent course material for use in graduate seminars on the subject.