In this talk I provide a broad overview of the range of phenomena that can be regarded as crosslinguistic effects. In addition to discussing the directions in which crosslinguistic effects have been found to occur, I describe the areas of performance that crosslinguistic effects encompass—from the overt transfer of forms and features from one language into another   and the transfer of how those forms and features are subsequently distributed in the learner’s use of the target language, to what happens in people’s brains while they are processing target-language structures that are similar versus unrelated to a language they already know, what they do with their eyes, faces, and hands while performing target-language tasks, what  they understand and what they remember during and after target-language tasks, what mental considerations they rely on when deciding how to refer to something in the target language, how quickly they can acquire the target language, which routes they take while doing so, and what levels of proficiency they ultimately reach. While describing the scope of crosslinguistic  effects, I also illustrate some of the innovative methods that are needed to investigate them, and I discuss the types of evidence necessary to establish that a given pattern of target-language performance truly is the outcome of crosslinguistic effects.