The prefrontal cortex (PFC) dopamine system plays an essential role in cognition, in-cluding working memory and cognitive flexibility and its dysregulation may contribute to the cognitive symptoms of psychiatric diseases like schizophrenia. Recordings of the dopamine release in the PFC show that it is released following both rewarding and aver-sive stimuli, with a bias toward aversive stimuli, but a detailed picture of how release depends on the valence of a stimulus remains an open problem. Here, we recorded PFC dopamine following a range rewarding, aversive and neutral stimuli, including painful stimuli, sucrose rewards, social interactions and novel objects. We find that dopamine release is strongly linked with the valence of the stimulus, with neutral stimuli triggering minimal release, even when they are surprising, and mice en-gage with them. To distinguish between possible models of PFC dopamine release, we examine responses to mixed-valence stimuli, which have both rewarding and aversive elements mixed together. We find that adding an aversive stimulus to a rewarding stimu-lus does not decrease dopamine release and in many cases increases release. We argue that PFC dopamine cannot depend on the net valence of a stimulus alone but is closer to the total valence of a signal. We discuss how such a signal may be important for PFC dopamine's role in shaping cognition.