Recent research in psychology, psychiatry and neuroscience has demonstrated reliable associations between temperament and individual differences in sensitivity and responsiveness to environmental cues and behavioral consequences. Temperament-influenced behavior patterns evident in infancy have also been found to predict behavioral tendencies in adulthood. Such observations suggest that neurophysiological structures and physiological events associated with temperament concepts exert a mediating or moderating influence between current environmental events and behavior. This paper summarizes relevant research on individual differences in sensitivity and responsiveness to environmental cues and behavioral consequences with reference to Jeffrey Gray's neuropsychological theory of temperament. Implications of temperament research for behavioral case formulation and therapy are described.