Market-based solutions at scale can make an impact upon many enduring social problems. Pioneering efforts are proliferating but many remain small-scale. What barriers prevent good business models from achieving scale, both at the enterprise level and in the wider ecosystem around the firm? What can social entrepreneurs, funders, intermediaries, and investors do to approach this challenge and help overcome these barriers? What actions or interventions accelerate the scaling of models that work? This session asks experts to address these ambitious questions.