This study sought to further elucidate the associations between psychopathy and the Fight-Flight-Freeze System (FFFS), Behavioral Inhibition System (BIS), and Behavioral Approach System (BAS) constructs in a large offender sample. More specifically, we examined whether individual differences in these systems would mediate the relationship between psychopathy and externalizing behavior. We used archival data from 823 male and female adult inmates, in which measurements of psychopathy, RST constructs, and externalizing behaviors were available. Path analyses showed that FFFS, over BIS or BAS, mediated the relationship between psychopathy and externalizing behavior. These results further underscore the important role that insensitivity to punishment plays in psychopathy. (C) 2014 Elsevier Ltd. All rights reserved.