The relationship between self-reported traumatic childhood experiences, cortisol levels, aggression, and psychopathy was investigated in prison inmates (n = 47) and healthy controls (n = 27). Besides questionnaires, a brief salivary diurnal profile was measured. Results show that criminals (both psychopaths and non-psychopaths) demonstrate more traumatic childhood experiences than the control group. Within the group of criminals, psychopaths showed the lowest diurnal cortisol concentrations, whereas the non-psychopaths demonstrated highest daily average cortisol (DAC) scores. High levels of aggression were related to traumatic childhood experiences in non-psychopaths and control participants, but not in psychopaths. Although psychopathic offenders demonstrated low levels of cortisol, high levels of childhood traumatic experiences and high levels of aggression, cortisol was not a mediating factor between childhood traumatic experiences and aggression. Implications of the finding that psychopathic offenders displayed lower and non-psychopaths showed higher daily cortisol levels are discussed.