The first contacts between linguistics and second language acquisition date from the period of contrastive analysis of languages, in the late 1960s and early 1970s. When contrastive analysis failed as an explanatory model, linguists lost interest in second language research and descriptive/contrastive studies declined, resulting in a changed research paradigm. Introduction of the term "interlanguage" marks the recognition of utterances of the second language learner as reflecting an underlying coherent language system. Two important aspects of interlanguage include: (1) markedness relations within the language system are relevant to language learning processes; and (2) a language system consists of different modules that interact during the language production process. However, these theories explain only certain phenomena within a complex system determining language behavior and language development of second language learners. The principle of universal grammar, which works from the assumption of an innate capacity for native language learning, offers a more useful framework for examining second language learning. Universal grammar research suggests that the linguistic relationship defined with this approach can account for phenomena such as coherence and order of acquisition in second language learning. A 66-item bibliography is included. (MSE)