Abstract: It is argued that a large portion of second language (L2) vocabulary knowledge is acquired incidentally in the sense that words are acquired as a natural by-product of children/learners performing everyday linguistics activities and tasks. However, the question of whether the majority of L2 words are acquired incidentally is a simplistic one as there is a number of issues that center around the process of incidental L2 vocabulary acquisition and for which agreed-upon answers cannot be cited. It is the purpose of the present paper to present an overview of the research on incidental L2 vocabulary acquisition, with a particular focus on issues related to incidental L2 vocabulary acquisition which have attracted the most attention in the field of L2 vocabulary research. Wherever possible, the implications of the research on incidental vocabulary acquisition for L2 pedagogy are discussed.