A 4-fold temperament typology was created by cross-classifying 4462 male US military veterans on MMPI indexes of behavioral inhibition and activation. Higher behavioral inhibition was associated with somewhat higher levels of cortisol, lower levels of social support, and a higher prevalence of lifetime generalized anxiety and major depressive disorders. Higher behavioral activation was associated with higher levels of testosterone, greater alcohol consumption and aggression, and a higher prevalence of alcohol, substance abuse, and antisocial personality disorders. The most pervasive dysfunction was indicated for a ''mixed'' subtype with both high inhibition and high activation, as these persons showed higher levels of testosterone, aggression, hostility, and alcohol consumption, as well as higher levels of both internalizing (e.g. major depression) and externalizing (e.g. ASP) lifetime psychiatric disorders.