Clinical observation, as well as epidemiological and research data, suggest that female gonadal hormones influence the course of panic disorder (PD). Panicogenic agents such as pentagastrin are useful tools with which to study the pathophysiology of panic attacks. Nine women with PD were randomly assigned to receive, in a crossover design, a 3-day pretreatment with medroxyprogesterone acetate (MP) prior to an injection of pentagastrin, and a 3-day pretreatment with a placebo prior to another injection of pentagastrin. The panic response and the anxiety response to pentagastrin were decreased after MP pretreatment. These preliminary results support the use of laboratory models for investigations of the interactions between progestins and anxiety.