This chapter reviews studies of word learning by normal adults and children, neuropsychological patients, and special developmental populations, which provide evidence that the phonological loop plays a crucial role in learning the novel phonological forms of new words. It suggests that the phonological loop component of working memory has evolved as a system for supporting language learning. The case of gifted language learners suggests that a natural talent for language learning may arise directly as a consequence of excellent phonological loop function. Learning the vocabulary of one's native language is one of the most important aspects of language acquisition. The chapter charts the consistently close relationships between phonological loop capacity and abilities to learn new words, either in natural vocabulary acquisition or in experimental simulations of vocabulary learning in individuals with short term memory (STM) deficits arising from brain damage, developmental disorders, and specific mental handicaps.