Operations research (OR) aims to improve health programs through scientific problem solving. OR was first used in WWII and later applied to health in the 1960s. OR involves 5 steps: 1) defining problems through data analysis, 2) selecting strategies to test, 3) experimenting with and evaluating strategies, 4) disseminating results, and 5) replicating successful strategies. Example OR topics include reducing HIV stigma, managing risky sexual behaviors, and improving quality of HIV care. OR studies test interventions through experimental, quasi-experimental, or non-experimental designs to measure impact on outcomes through data collection methods like surveys, interviews and observations.