This paper discusses some possibilities and limitations of laboratory research methods for testing theories of second language acquisition. The paper includes a review of 20 experimental lab studies. The review focuses on the motivation for conducting lab studies, the use of artificial or semiartificial language structures, and various design features (including pre- and posttesting, number of subjects, random subject assignment, between- and within-subjects comparisons, treatment materials and procedures). The paper calls for lab studies addressing issues central to SLA theory (“learning” vs. “acquisition”) and ends with some methodological recommendations, concerning the length of experimental treatments, the use of grammaticality judgment tasks, the measurement of reaction times, and the use of retrospective interviews.