Disaster workers as well as victims are at increased risk for acute stress disorder (ASD). The present study was undertaken to study the course of the stress response in a group 187 young, male military personnel who served as rescue workers for 3 days after an earthquake in central Taiwan. A control group of 83 young, male military personnel who remained on the base was also studied. The initial evaluation took place within 16 days of the earthquake. Participants were interviewed using the Mini International Neuropsychological Interview. Thirty-one individuals met DSM-IV criteria for ASD at the initial evaluation. These 31 individuals were interviewed a second time 1 month after the earthquake. Plasma samples were also collected and assayed for nitric oxide (NO). The point prevalence rates of ASD 2 weeks after the earthquake in the initial evaluation were 9 and 16% in the rescue worker and control groups, respectively. At 1 month, the prevalence was substantially lower, in the range of 2-3%. Significant inverse correlations were observed between severity of stress symptoms and the plasma concentration of NO in the rescue worker group (r=-0.36 to -0.64, n=17, P<0.05). We conclude that young military personnel without formal training in rescue operations are at risk for ASD, but their risk appears to be no higher than that in a similarly composed control group of young military personnel. Longitudinal studies with plasma measures of NO are needed to clarify its potential role in the development and course of ASD and related syndromes.