The present study investigated the transfer of induced happy and sad mood functions through equivalence relations. Sixteen subjects participated in a combined equivalence and mood induction procedure. In Phase 1, all subjects were trained in 2 conditional discriminations using a matching-to-sample format (i.e., A 1-B1, A2-B2, A 1-C1 , A2-C2). In Phase 2, they were tested for the formation of symmetry (i.e., B1-A 1, B2-A2, C1-A 1, C2-A2), and equivalence relations (i.e. , B1 -C1 , B2-C2, C1-B1, C2-B2) . In Phase 3, a musical mood induction procedure was employed to induce happy and sad mood states in the presence of the B stimuli. Eight subjects were exposed to happy music in the presence of B1, and sad music in the presence of B2, and for the other 8 subjects, this mood induction was reversed. In Phase 4, subjects were exposed to a mood functions test to determine whether the appropriate mood functions had been established with the B stimuli. In Phase 5, they were exposed to a transfer of mood functions test to determine whether the appropriate happy and sad mood functions had transferred via equivalence from the B stimuli to the C stimuli. The mood measures showed that the specific mood functions established in the prese,nce of the B stimuli successfully transferred to the C stimuli for the majority of subjects. This transfer of mood function effect is discussed in terms of its implications for a behavioral understanding of mood changes.Stimulus equivalence has generated a great deal of empirical and theoretical interest amongst the behavior-analytic community in the last two decades. The fundamental feature of the equivalence phenomenon is that it demonstrates the emergence of novel forms of derived stimulus control that are not readily explained by the three-term contingency This work was prepared wh ile Yvonne Barnes-Holmes was funded by the National University of Ireland , Maynooth . We thank Erik Arntzen and an anonymous reviewer for their constructive and helpful comments on an earlier version of the current work. Correspondence should be directed to