OBJECTIVES/SPECIFIC AIMS: The primary aim of this study is to conduct a within-child comparison of in-school PA while attending nature-based and traditional preschool programs. The secondary aim is to observe the types of activities performed at each preschool location to determine which activities lead to greater and lesser amounts of school-based PA. METHODS/STUDY POPULATION: This will be a within-subjects repeated measures study in which participants will be recruited from a single preschool program where they spend two days per week (Monday/Wednesday) at a nature-based site, and two days per week (Tuesday/Thursday) at a traditional preschool location. All participants will be outfitted with a waist-worn Actigraph GT3X accelerometer, which they will wear from the moment they arrive to their preschool location until the moment they leave. Measurements will be conducted for four consecutive school days across two separate measurement periods, once in the winter and once in the spring. Additionally, a trained researcher will be present for the entirety of each measured day to document the types of activities participants engage in throughout the day, when these activities occur, and for how long. Accelerometer data will be analyzed using total counts, a reflection of total PA across all intensities, to determine school-based PA. Total activity counts will also be reduced to counts per minute and cross referenced with direct observation data to determine which activities contribute to higher and lower periods of PA throughout the day. Within child comparisons using two-tailed t-tests be made at both measurement periods between both preschool sites to determine whether significant differences in PA levels exist in children while attending either a nature-based or traditional preschool program. Logistic regression will also be applied to assess variables contributing to children’s PA including, preschool location, weather, and time spent outside. RESULTS/ANTICIPATED RESULTS:. It is hypothesized that preschool children will engage in significantly more PA while attending a nature-based preschool program compared to a traditional preschool classroom setting. Opportunities for free and unstructured play will be greater in a nature-based setting compared to a traditional preschool location. Time spent outdoors will be the determining difference between preschool children’s PA behaviors at a nature-based versus traditional preschool program. Variations in PA levels as a result of seasonal weather differences will be minimized on days in which children attend a nature-based preschool program. DISCUSSION/SIGNIFICANCE OF IMPACT: To our knowledge, this will be one of the first studies conducting a within child comparison of preschool-aged children’s PA levels between a nature-based and traditional classroom setting. If, as hypothesized children engage in significantly more PA while attending their nature-based preschool program, the comparison to their traditional preschool site will provide insight into the magnitude of differences and where these differences in PA behaviors may occur throughout the school day. This information may then be used to inform future intervention’s focusing on better aligning children’s PA levels in a traditional school setting with what might be achieved through a nature-based educational program.