We study quality upgrading in informal markets through two experiments with street-food vendors and consumers in India. First, we define quality in terms of food safety and develop a context-specific measurement framework. Second, we show that consumers are willing to pay substantial premiums for cleanliness. Third, we implement a vendor-level intervention that lowers upgrading costs and enhances the ability to signal quality through sanitation-related equipment. The intervention improves food-safety practices and profits, but effects are modest and fade over time. Fixed pricing norms and local environmental constraints appear central, consistent with a moral hazard model where cleanliness is not profitable.