This journal article describes a study that used ecological momentary assessments (EMAs) to examine real-time factors to determine the predictors of sexual activity among homeless youth given the disproportionately high prevalence of HIV infection among this population (homeless youth are six to 12 times more likely to become infected with HIV than housed youth). The researchers recruited 66 youth experiencing homelessness, ages 18 to 24, from a drop-in center in Houston, Texas. The participants were issued mobile phones that prompted brief EMAs five times a day for 21 days. The EMA items assessed near real-time sexual behaviors, thoughts, stress, emotions, and environmental factors. The findings showed that 70 percent of participants were sexually active during the reporting period and many engaged in high-risk behaviors such as having unprotected sex and sharing needles while injecting drugs. The researchers conclude that using real-time EMA data was successful in predicting sexual intercourse among the sample of predominately unsheltered homeless youth. They found that sexual urge and drug use accounts for increased odds of engaging in sexual activity on any given day; therefore, interventions targeting sexual urge and drug use may help predict sexual activity among a population at high risk for HIV.