We used the startle eye blink paradigm to investigate the processes underlying physiological responding to concealed information. Autonomic responding was measured together with eye blink responses to startle probes presented during mock crime and control pictures. Based upon 'orienting theory', greater startle modulation to crime pictures in comparison to control pictures was expected. The electrodermal, heart rate and respiratory changes in Experiment 1 (n=29) showed enhanced orienting to the crime pictures, but we observed reduced rather than enhanced startle modulation. In Experiment 2 (n=91) and Experiment 3 (n=38), participants either were or were not instructed to inhibit physiological responding in order to test whether inhibition was an explanation for the pattern of startle blink responding. Reduced startle modulation was observed only when participants inhibited physiological responding, confirming the proposed role of inhibition. The data suggest that not only orienting, but also inhibition contributes to physiological responding to concealed information.