The hallmark of generalized anxiety disorder (GAD) is chronic uncontrollable worry. A preattentive bias toward threat cues and hypervigilance may support this ongoing state of apprehension. A study was conducted to bridge the attentional and physiological underpinnings of GAD by examining phasic heart period (HP) responses to cued threat and nonthreat stimuli. Thirty-three GAD clients and 33 nonanxious control participants engaged in an S1-S2 procedure that employed cued threat and nonthreat word stimuli, during which phasic HP reactions were recorded. As compared with the control group, the GAD group showed (1) smaller cardiac orienting responses and impaired habituation of cardiac orienting to neutral words, (2) HR acceleration in response to threat words, and (3) a conditioned anticipatory HR deceleration to threat words over repeated trials. The cardiac-autonomic underpinnings of GAD appear to rigidly maintain precognitive defensive responses against threat. This portrayal is discussed in the context of an integrative model that depicts diminished global adaptive variability in GAD.