This paper discusses some possibilities and limitations of laboratory research methods fortesting theories of second language acquisition. The paper includes a review of 20 experimentallab studies. The review focuses on the motivation for conducting lab studies, the use of artificialor 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 toSLA theory (“learning” vs. “acquisition”) and ends with somemethodological recommendations, concerning the length of experimental treatments, the use ofgrammaticality judgment tasks, the measurement of reaction times, and the use of retrospectiveinterviews.