Participants will be provided with a link to download PTSD Coach (freely available on iTunes and Google Play Stores or through myvaapps.com) and brief recommendations for how to use the app over the subsequent 8 weeks of the study. PTSD Coach is a mobile app for iPhone and Android, developed by the VA National Center for PTSD in collaboration with National Center for Telehealth and Technology (T2) and the Department of Veterans Affairs Patient Care Services. PTSD Coach was initially developed and launched in March, 2011, with usability and focus group data derived from a sample of 80 veterans with PTSD, many of whom were explicitly requesting "something I can do when I'm stressed, wherever I am." The app provides 4 primary treatment components: 1) psychoeducation about PTSD, 2) self-monitoring tools, 3) immediate tools for symptom management, and 4) immediate access to public and private support resources. The psychoeducation component provides text and audio informational topics about PTSD, with an emphasis on normalizing the condition, and information about ways to begin engaging with mental health services. The self-monitoring tools component administers the PTSD Checklist Civilian version (PCL-C), provides tailored feedback on symptom level and changes since the last assessment, and allows and encourages users to create reminders to self-monitor their symptom levels. The symptom management component provides specific tools tailored for managing reminders of trauma, avoiding trauma-related triggers, overcoming feelings of being disconnected from others, overcoming feelings of being disconnected from reality,improving sleep, and reducing feelings of sadness, hopelessness, worry, anxiety, or anger.These tools include audio-based relaxation exercises, guided deep breathing, making plans for social activities, engaging in pleasant activities, tips for distraction from unpleasant sensations, and other simple exercises. The support component encourages users to create a personal support network (from their phone's contact list) and provides users with information about additional resources for veterans (e.g., crisis and help-line numbers). Evidence for PTSD Coach is described in detail in the Preliminary Studies section. In brief, use of PTSD Coach alone is associated with significant within-session changes in ratings ofdistress43 and demonstrates a small but clinically meaningful effect on PTSD symptoms(d=.30, f~.15) relative to a wait-list control group.