The symptoms of posttraumatic stress disorder and associated risk factors were investigated among health care workers in earthquake-affected areas in southwest China. 343 health care workers completed the Chinese version of the Impact of Event Scale-Revised 3 mo. after the Wenchuan Earthquake. The prevalence of probable PTSD was 19%. The significant risk factors identified for PTSD severity included being female, being bereaved, being injured, and higher intensity of initial fear. These findings suggest that PTSD is a common mental health problem among health care workers in earthquake-affected areas. The present information can be useful in directing, strengthening, and evaluating disaster-related mental health needs and interventions after an earthquake.