We performed an open-label single-institution phase II trial of mirtazapine (15-30 mg by mouth [po] every day [qd]), a tetracyclic antidepressant that may lead to weight gain, for 8 weeks in nondepressed patients with cancer-related cachexia/anorexia (CRCA). The primary end point was the proportion of patients who gained > or =1 kg at week 4. Secondary end points were quality of life and appetite. From June 2006 to July 2007, 17 of 58 eligible patients were enrolled. On intention-to-treat analysis at week 4, 4 of 17 patients (24%) gained 1 kg or more, 1 patient maintained weight (gain of 400 g) and 2 patients lost weight (800 g and 1.2 kg); 24% and 6% improved appetite and health-related quality of life (HQOL), respectively. Mirtazapine is a promising agent for the treatment of CRCA.