The undoing hypothesis proposes that positive emotions serve to undo sympathetic arousal related to negative emotions and stress. However, a recent qualitative review challenged the undoing effect by presenting conflicting results. To address this issue quantitatively, we conducted a meta-analytic review of 16 studies ( N = 1,220; 72 effect sizes) measuring sympathetic recovery during elicited positive emotions and neutral conditions. Findings indicated that in most cases, positive emotions did not speed sympathetic recovery compared to neutral conditions. However, when a (...) composite index of cardiovascular reactivity was used, undoing effects were evident. Our findings suggest the need for further work on the functions of positive emotions. (shrink)