This presentation describes the first formal effort to examine the implementation and impact of communities of practice (CoP) in two large initiatives funded by the Lumina Foundation. This panel describes the work of two evaluators who collaborated to develop a common analytical framework based on Realistic Evaluation, with one evaluator also using Cultural Historical Activity Theory (CHAT) to analyze implementation, perceptions, and contribution of the CoPs to the work. The evaluation officer who oversaw the initiative at the Lumina Foundation discussed the implications of the evaluation for both efforts and for the overall work of the foundation.#realist_evaluation #community_of_practice_(CoP) #2010Conference