Despite the central status of avoidance in explaining the etiology and maintenance of anxiety disorders, surprisingly little behavioral research has been conducted on human avoidance. In the present paper, first we provide a brief review of the empirical literature on avoidance. Next, we describe the implications of research on derived relational responding and the transformation of functions for a contemporary behavioral account of avoidance, before providing several illustrative research examples of laboratory-based analogues of key clinical treatment processes. Finally, we suggest some challenges and opportunities that lie ahead for behavioral research on anxiety and avoidance. (Contains 1 figure.)