Ancient sources present mainly two Stoic definitions of passion: as an irrational and unnatural movement of the soul, and as an excessive impulse. These definitions hold for the Stoics in general, and undoubtedly for Zeno. However, in other sources, passion is seen as a judgment or as what supervenes on judgment. In this case, some sources refer to Zeno, others to Chrysippus, and still others do not refer to any particular Stoic philosopher, so it is unclear whether the idea of judgment was already present in Zeno or is an innovation of his successor. Starting from this problem, I attempt to reconstruct the meaning of Stoic passion, with a particular interest in the definition of passion as judgment. In this way I will try to show that the apparently different positions of Zeno and Chrysippus are in fact the same when viewed within the framework of the Stoic theory of action.