In this article we discuss the role of desirable difficulties in vocabulary learning from two perspectives, one having to do with identifying conditions of learning that impose initial challenges to the learner but then benefit later retention and transfer, and the other having to do with the role of certain difficulties that are intrinsic to language processes, are engaged during word learning, and reflect how language is understood and produced. From each perspective we discuss evidence that supports the notion that difficulties in learning and imposed costs to language processing may produce benefits because they are likely to increase conceptual understanding. We then consider the consequences of these processes for actual second-language learning and suggest that some of the domain-general cognitive advantages that have been reported for proficient bilinguals may reflect difficulties imposed by the learning process, and by the requirement to negotiate cross-language competition, that are broadly desirable. As Alice Healy and her collaborators were perhaps the first to demonstrate, research on desirable difficulties in vocabulary and language learning holds the promise of bringing together research traditions on memory and language that have much to offer each other.Vocabulary learning, viewed broadly, is fundamental to our initial and continued learning in almost every domain. We need to know the language, so to speak, not simply in the sense of learning a first or second language but also in the sense of learning the vocabulary that characterizes some field of study, such as biology or the law. Our primary concern as teachers, for example, may be increasing students' higher-level understanding of concepts in some domain and increasing their ability to generalize those concepts to new situations where they are relevant, but achieving those goals rests on students having acquired the basic vocabulary of terms and labels in that domain.Perhaps understandably, then, vocabulary learning has often been examined in different ways by memory researchers and by language researchers. Memory researchers have frequently examined vocabulary learning using materials that are selected to ensure that the participants know little, typically nothing, of the to-be-learned language, such as having college students learn English translations of Swahili words, before the experiment. The goals of such experiments are to understand more about processes such as response learning,