Panic disorder (PD) is characterized by a fear of panic-related sensations that leads to significant anxiety about the occurrence of future panic attacks and/or avoidance of situations that could trigger further attacks. Similar to other anxiety disorders, PD is substantially more common in women. In addition, there is some evidence of differences in the presentations and consequences of PD among men and women. This entry explores the environmental, biological, and psychological reasons underlying such sex differences. In addition, it examines the role that gender characteristics play in the development of PD. The entry concludes by discussing the implications of such gender and sex differences for the treatment of this disorder.