There is considerable psychophysiological evidence to indicate that the left and right halves of the human forebrain differentially associate with particular emotions and affective traits. A neurobiological model is needed. Here I propose that forebrain emotional asymmetry is anatomically based on an asymmetrical representation of homeostatic activity that originates from asymmetries in the peripheral autonomic nervous system. This proposal builds on recent evidence indicating that lateralized, higher-order re-representations of homeostatic sensory activity provide a foundation for subjective human feelings. It can subsume differing views of emotion and the forebrain because it suggests that emotions are organized according to the fundamental principle of autonomic opponency for the management of physical and mental energy.