Obesity prevention is critically important for population health, yet remains a complex undertaking. The causes of obesity are varied and exist throughout multiple interconnected spheres of influence. Interventions and their evaluations must take this complexity into account to obtain meaningful results. We present the evaluation strategies of two distinct efforts to reduce and prevent obesity in the Chicago area through policy and environmental changes. Both interventions were designed to be implemented by multiple organizations working independently toward project goals and tailoring activities to specific local conditions. Each project had a unique evaluation strategy but both used mixed methods to collect process and outcome data. With projects that call for customization of interventions, it is important to provide a complete picture of the context, intervention and outcomes through detailed implementation data. Layering of outcomes data from various levels (individual, institutional, community) is important for a meaningful and comprehensive evaluation.#HealthEvaluation #eval14 #2014Conference