This article offers a critical review of the existing literature on gains in a second language (L2) as a result of a study abroad (SA) experience. The aim of this article is (a) to provide an updated overview of the empirical evidence of L2 gains emerging during an SA experience in order to know what the current situation is, and (b) to identify gaps in the research on SA and evaluate where further research is needed in this area. Issues related to the SA participants' age, background, initial L2 proficiency level, length of stay (LoS) in the L2 country, duration of the effects of these SA experiences, and cognitive skills have been identified as crucial factors to be taken into account when carrying out research on SA as well as when drawing conclusions from the current empirical evidence. (Contains 2 figures and 1 table.)