This paper discusses error analysis as one source of evidence for an overall theory of second language acquisition. Four related areas which form the context for error analysis are discussed in relation to second language learning and the goals and methodology of error analysis; (1) theories of the nature of language which determine theories of error analysis; (2) the study of language systems in contact, which seems to indicate that syntax is subordinate to semantics; (3) the learning of linguistic systems, divided into learning the code (sentence) and learning how to use the code; and (4) the use of linguistic systems in communication, concerned with the nature of the learner's "utterances," in contrast to "sentences." Although the present study is not considered definitive, it is believed that with further study error analysis will greatly influence attitudes toward language-teaching problems. (AM)