Preventing prescription opioid misuse among employees working in high risk industries. - Abstract 11.8 million Americans aged 12 or older reported opioid misuse in 2016. Over 40,000 people died due to opioid-related overdoses in 2016, up 345% from 2001 to 2016. Prescription opioids have historically served as an onboarding ramp to drugs with a high-risk of overdose, including heroin and the highly potent and accessible, fentanyl. Strikingly, 21 to 29 percent of patients prescribed opioids for chronic pain misuse or overuse them and individuals with a history of prescription opioid abuse are 40 times more likely to abuse heroin. In the workplace, prescription opioids for pain made up an average of 85% of prescribed pain medications according to state-level workers’ compensation claims, and injured workers are issued opioid prescriptions at a rate three times the national average. Construction trade workers, a 95.9% male-dominated industry, exhibit the highest rates of opioid dispensing in workers’ compensation claims and registered nurses and certified nursing assistants, made up of 90% women, report the greatest number of non-fatal work-related injuries. To date, no evidence-based interventions targeting industries with a high-risk for prescription opioid misuse and/or overuse, based on injury and prescribing rates, exist. Thus, there is a critical need for an engaging, scalable, evidence-based intervention for the prevention of prescription opioid misuse and/or overuse among high-risk workforce populations, namely, construction trade workers and employees in nursing. Evidence-based mHealth interventions are an effective intervention delivery method for high-risk health behavior interventions. The objective of this proposed research is to develop an optimized, highly effective, mHealth intervention designed to prevent prescription opioid use among workers in industries with a high risk for injury and opioid prescribing. The research and development performed in the proposed Phase II project will result in a fully designed, optimized, and evaluated, market-ready product to be implemented among high- risk industries. The specific aims of this study are to 1) Develop the remaining two fully functional intervention components targeting motivational factors associated with intentions to use prescription opioid medications for pain; 2) Optimize and evaluate the intervention lessons. At the completion of the proposed research and development, our expected outcome is to have demonstrated scientific and technical merit for the first evidence-based intervention for preventing prescription opioid misuse and/or overuse among workers of high- risk industries.