This article examines medico-legal and popular interpretations of suicide in early twentieth-century Lima. In this period, often referred to as the Aristocratic Republic, physicians and lawyers interpreted suicide through the lens of modern scientific and legal thought and came to challenge the traditional interpretations of the Church, which insisted that suicide was a voluntary act. For these groups, suicide, almost invariably an act of madness, was essentially a modern phenomenon, both product and evidence of Lima's growing “modernity,” as well as a social disease that could be combated by adopting adequate policies. However, though they opposed the Church's insistence on the responsibility of the suicide, physicians and lawyers viewed the propensity to suicide as evidence of the moral and racial degeneration of Lima's population and shared the Church's condemnation of suicide as a shameful and immoral act. For ordinary people, medico-legal discourse on suicide provided an additional explanation for self-death. In particular, the idea that suicide was caused by forces over which no one had any real control, especially forces that were a product of the perceived “modernization” of Lima, such as neurasthenia (a nervous condition that became a widespread explanation for suicide at the time) helped in the need to dilute blame and guilt. But, although medico-legal and popular understandings of suicide cross-fertilized, attempts by ordinary people to apportion certain meanings to suicide, particularly those that constructed suicide as a voluntary act, were perceived by the medico-legal community, and, indeed, more broadly, as threats to society.