Consultation by mail had been common in medical practice more or less since the time of its consolidation in Europe in the twelfth and thirteenth centuries, but this mode of communication vastly expanded in the seventeenth and eighteenth centuries. Analyzing a group of letters sent to the Spanish court physician Juan Muñoz y Peralta (1665–1746) by his patients, this article shows how these patients, far from being passive, were actively involved in elaborating medical knowledge and in making decisions about therapeutic strategies for their own treatment. Our main aim is to focus attention on these nonprofessional voices, on the words of patients themselves or those who, like them, were not trained in medicine. Approaching our subject through this interpretative framework, we provide an example of medical-cultural analysis that documents voices belonging to patients who were active in considering, interpreting, and treating disease in an effort to have control over their own bodies. Their voices should be taken into account when writing a cultural history of early modern medicine.