A general theory of heritable personality traits and their neurobiological basis is described. Three independent dimensions of personality are defined and related to heritable variation in patterns of response to specific types of environmental stimuli: 'novelty seeking' is due to a heritable tendency toward frequent exploratory activity and intense excitement in response to novel stimuli; 'harm avoidance' is due to a heritable tendency to respond intensely to aversive stimuli and to learn to avoid punishment, novelty, and non-reward passively; and 'reward dependence' is due to a heritable tendency to respond intensely to reward and succorance and to learn to maintain rewarded behavior. Evidence suggests that variation in each dimension is strongly correlated with activity in a specific central monoaminergic pathway: novelty seeking with low basal dopaminergic activity, harm avoidance with high serotonergic activity, and reward dependence with low basal noradrenergic activity. These neurobiological dimensions interact to give rise to integrated patterns of differential responses to punishment, reward, and novelty. The combination of high novelty seeking, high reward dependence, and low harm avoidance (histrionic personality) or the combination of high harm avoidance, low reward dependence, and low novelty seeking (obsessional personality) are each associated with information-processing patterns that lead to unreliable discrimination of safe and dangerous situations and hence to chronic anxiety. In individuals with high novelty seeking, chronic anxiety is characterized by global uneasiness or alarm without specific premonitory cues, frequent bodily pains due to low pain and sensation thresholds, low sedation threshold, and slow fatigability. In contrast, in individuals with high harm avoidance, chronic anxiety is characterized by frequent anticipatory worries based on specific cues, high pain and sedation thresholds, and easy fatigability. In response to frustrative non-reward, individuals with high reward dependence are susceptible to compensatory noradrenergic hyperactivity and hence acute or recurrent states of agitated dysphoria associated with reward-seeking behaviors such as overeating and increased sexual activity. Specific predictions are made about normal personality development as well as the development and familial aggregation of anxiety, somatoform, depressive and personality disorders. These predictions are compared with available information, and recommendations are made for future research.