The startle reflex can be modified by cognitive and affective variables. The present study investigated startle responses in 12 patients with panic disorder, 22 patients with social phobia and 15 healthy controls. The eye-blink component of the acoustic startle reflex was measured during baseline, pulse-alone, pre-pulse and fear-potentiated startle to disorder-specific threat words. Results indicated that patients with panic disorder exhibited significantly larger startle response amplitudes during baseline, pulsealone, pre-pulse and fear-potentiated trials than did healthy controls. Startle response amplitudes of patients with social phobia differed from healthy controls at effects of similar magnitude as the effects seen for patients with panic disorder, for all types of startle trials. During fear-potentiated trials, all groups exhibited largest startle amplitudes following the presentation of physical threat-related words, second largest magnitude to social threat-related words and the smallest to non-threatening words. It is recommended that future studies further examine startle response parameters in all forms of anxiety disorders.