Research over the past decade has advanced our understanding of the neuroanatomical and neurochemical substrates of anxiety disorders, including panic disorder. For example, the results of challenge studies with a variety of panicogenic agents that operate by diverse pharmacologic mechanisms have suggested a network model of panic involving dysregulation of multiple neuronal systems. Genetic analyses are consistent with a heritable predisposition, or "panic diathesis," that confers an increased susceptibility to pharmacologic challenge, even in subjects with no overt history of panic disorder. Functional imaging studies confirm preclinical investigations of the anatomical basis of anxiety and provide further evidence for a network of related brain regions mediating the genesis of anxious and fearful behaviors, including panic attacks. Taken together, this research offers a theoretical framework for the ongoing development of improved diagnostic and treatment options.