Background The aim of this study was to investigate the potential use of mirtazapine in Korean veterans diagnosed with PTSD, by comparing it with sertraline, a drug approved for use in PTSD in the USA. Methods Efficacy was evaluated by the clinician administered PTSD scale (CAPS-2), the Hamilton rating scale for depression (HAMD-17) and the clinical global impression scale (CGI), at baseline and at weeks 1, 2 and 6. A response was defined as a greater than or equal to30% decrease in CAPS-2 total severity, a greater than or equal to50% decrease in total HAMD-17 score, and a CGI-I score <3. Results 51 patients on mirtazapine (mean age/duration of illness: 59.1/33.5 years) and 49 on sertraline (mean age/duration of illness: 60.6/35.6 years) completed the study. The mean daily dosage was 34.1 mg for mirtazapine and 101.5 mg for sertraline. On the CAPS-2 total score more patients responded in the mirtazapine group at week 1 (13 vs 2%) and week 2 (51 vs 31%). At week 6 this difference was statistically significant (88% vs 69%, p = 0.039) on the CAPS-2 total score. The HAMD-17 total score and CGI-I score decreased in both groups, with no significant differences between th groups on all time points. The main side effects for the mirtazapine group were: dry mouth (19.6%), constipation (19.6%), somnolence (15.7%) and weight gain (1.96%); and for the sertraline group: indigestion (14.3%), palpitation (6.1%), agitation (2.0%), epigastric soreness (2.0%), insomnia (2.0%) and sexual dysfunction (2.0%). Conclusion Mirtazapine appeared to be an effective and well-tolerated treatment for PTSD in Korean veterans. Copyright (C) 2004 John Wiley Sons, Ltd.