The present study investigated whether patients with panic disorder had an increase in the startle response and whether this effect, if present, was specific to anticipatory anxiety. The eyeblink component of the acoustic startle reflex was measured in a paradigm involving the anticipation of electric shocks (fear-potentiated startle) in 34 patients with panic disorder and 49 healthy controls. Startle was also recorded in the absence of specific threat at the beginning and at the end of the testing. The testing consisted of three phases: adaptation, fear-potentiated startle, and recovery. In the adaptation and recovery phases, startle stimuli were delivered in the absence of threat. In the fear-potentiated startle phase, startle stimuli were delivered in threat conditions, when subjects anticipated shocks, and in safe conditions that predicted the absence of shocks. Startle was larger in the younger patients (age < 40 years old) compared to the younger controls throughout the testing. The difference reached significance only during the fear-potentiated startle phase, however. Startle was nonsignificantly reduced in the older patients (age > or = 39 years old), compared to the older controls. The results are discussed in terms of the contextual effects of the experimental setting.