The Mobile SMASH study is our flagship work in which we're using mobile devices to study the situational influences on sexual decision-making. Using intensive longitudinal methods called ecological momentary assessment (EMA), this research collects both passive and self-report data about a variety of factors over time, such as contexts (e.g., social/physical environment), cognitive and emotional states, and other behaviors (e.g., alcohol/drug use). The goal is to explore the potential role these factors play in increasing risk for sexually-transmitted infections like HIV, and ultimately to identify a concise set of momentary risk factors that could be useful in forecasting when risk might occur, so that brief interventions can be delivered via mobile devices at the right time ("just in time" interventions).