Abstract This project will iteratively develop and test a playable prototype of an interactive web-based handwashing game to improve hand hygiene for elementary school-age children. The commercially released game will be playable on smartphones, tablets, or notebooks, and will emphasize (1) how to wash--proper technique and duration; (2) when to wash--before meals and after visits to the restroom; and (3) consistent application--establishment and maintenance of good hygiene habits. All three components are necessary for effective hand hygiene. Aim 1: Iterative Design. The project team will work with educational technology and clinical experts as co-designers to develop a playable prototype game. The researchers will investigate the usability, engagement, and child focus on key content. Aim 2: Pilot Study. The developed intervention will be tried in a randomized control trial with elementary school children attending after school programs, who have not seen the game before, compared to a control group of children who attend the same after-school program, but do not receive the learning game intervention. Pre- and post-test improvement in hand hygiene technique will be tested with a handwashing trial using UV-fluorescent ink, image capture of washed hands, and quantification of ink remaining after washing. Potential customers include after-school programs, school districts, as well as pediatric and family medicine clinics, that seek infection control measures for hand hygiene that are effective, save provider or teacher time, and target both English and Spanish speaking students and their families.