The legend of Los siete infantes de Lara as redacted in the Estoria de España and Crónica de 1344 stands out from other extant Castilian epics in its focus on cross-border alliances and relationships with al-Andalus, as well as its positive characterization of Muslim Andalusi characters. This article focuses on the obverse of this dynamic and suggests that their favorable portrayal is in fact one of several literary devices that work to emphasize the degenerate behavior of their Castilian counterparts; a critique that heightens from one chronicle to the next and is at times expressed by way of irony. The legend presents a panorama of different Castilian masculinities, from young mozos to established members of the nobility, all of whom exhibit toxic behavioral patterns that have pathological, violent outcomes. This toxicity takes hold in different ways, from an inability to control their pasiones to a covetous pursuit of power and wealth. Their behavior explicitly contradicts the mesura and moral benevolence advocated by theoretical [End Page 41] models of masculinity formulated from the classical era to the early fourteenth century, as well as the established therapeutic tradition in medieval medical texts.