The diffusion of Lutheran ideas began in France in the 1520s. In the Provence, the authorities became aware of the danger posed by the heretics only in the early 1530s with the discovery of the presence of the Waldensians in the Luberon, though they had already settled there a long time ago, and by the growing emergence of Lutheran dissent throughout their province. How is it possible to recognize a heretic, or at least to have sufficient suspicions to be able to denounce him or her? And on what charge can the courts summon a person to appear before it? This is the topic addressed in this article, which analyzes the period up to 1560 due to the changed context elicited by the so-called Wars of Religion.