ABSTRACT The authors hypothesized that a greater degree of stimulus-response variability could either serve adaptive or maladaptive control purposes, depending on levels of Neuroticism. Specifically, a more variable relation between stimulus and response may be emotionally beneficial if such flexibility is used to support non-neurotic forms of self-regulation, but costly if it is used to support neurotic forms of self-regulation. To investigate these ideas, the authors asked 232 college undergraduates within three studies to perform several choice reaction time (RT) tasks. On the basis of performance, we could quantify stimulus-response variability in terms of RT variability from trial to trial. Such a measure of stimulus-response variability interacted with Neuroticism in predicting momentary negative affect (Study 1), informant judgments of negative affect (Study 2), and informant judgments of anxious symptoms (Study 3). As hypothesized, greater stimulus-response variability tended to be associated with less distress among individuals low in Neuroticism, but more distress among individuals high in Neuroticism. The results highlight the manner in which Neuroticism may “taint” control functions, in turn reinforcing Neuroticism-linked outcomes.