PTSD is common after combat, but onset is frequently delayed until months after return. This “honeymoon effect” affords opportunities to prevent PTSD if high-risk individuals can be identified. We report our iterative effort to educate military family members to recognize symptoms and facilitate intervention, along with preliminary results from direct longitudinal assessment of returning service members for development of PTSD. We conducted focus groups with military families and incorporated their feedback into an educational website which we piloted before evaluating PTSD-related knowledge with a 25-item questionnaire in 497 military family members before and after their use of the website. We also documented interventions reported by 217 of the family members, who, subsequently, returned to the site. In a separate ongoing study, we are assessing 100 service members within 2 months of return from combat with novel brain imaging, psychophysiology, genetic and neuroendocrine measures, followed by serial evaluations to identify the baseline measures that best predict subsequent PTSD. Our educational website improved PTSD-related knowledge from a mean 13.9 correct responses beforehand to 18.7 after (p < .001; effect size 1.2). Nearly 60% of family members returning to the site had intervened with a service member; 74% of them reported discussion with the service member about their symptoms was helpful, as did 91% who persuaded them to see a healthcare provider. Preliminary analysis of the direct assessment of service members indicates that psychophysiologic measures are significantly different between those with subthreshold symptoms of PTSD versus those with very few PTSD symptoms. A web-based intervention can improve PTSD-related knowledge and foster behavioral changes in military family members. Risk stratification of service members via assessment upon their return from deployment also has the potential to facilitate targeted interventions. While others have developed PTSD-related educational websites, we believe we are the first to document their efficacy, both with regard to knowledge and behavioral enhancement. Our direct assessment of service members is unique in its comprehensiveness, and holds great promise for risk stratification.