In this open label pilot study, we studied the efficacy of mirtazapine (Remeron) in panic disorder. Twenty-eight patients with a DSM-IV diagnosis of panic disorder, with or without agoraphobia (10 males/18 females), were included and 19 patients completed the study. The 15-week trial started with a 3-week single-blind placebo run-in period. After this run-in period, the 12-week active treatment phase started. As primary efficacy measures, we studied the decrease in the number of full symptom panic attacks and the number of patients completely free of panic during the last 3 weeks of the study. Seventy-four percent of the patients were considered responders, according to a decrease of at least 50% in panic attack frequency. All primary and secondary efficacy measures showed a significant improvement from the second week of active treatment onwards to endpoint. The main side-effects were different from the usual side-effects in selective serotonin reuptake inhibitors (SSRIs) (initial drowsiness, weight gain and pain in the legs). The results of this open label study in panic disorder suggest that mirtazapine seems to be a fast and effective treatment alternative for SSRIs in panic disorder.