This paper outlines the rise of collections of medical observationes and case reports as a major literary genre of medical writing from the mid-sixteenth century onwards. It distinguishes two principal subgenres which both reflected the growing appreciation of empirical knowledge in Renaissance medicine but served very different functions. Case reports from ordinary medical practice, the Curationes and Observationes medicae fulfilled an important didactic function. Covering the whole range of diseases that (future) physicians might encounter, they showed how the author, usually an experienced physician, who had already seen and cured numerous patients, diagnosed and treated complex and difficult cases. In most cases, the author’s diagnosis proved correct and his treatment successful, and his report could thus serve as a model for the treatment of similar cases in the reader’s own practice. Some authors also added a learned scholion to offer a theoretical explanation and help generalize their findings and conclusions and, more rarely, an autopsy report, when the treatment failed (though certainly not due to an error on the author’s part). Natural historical observations, by contrast, the second major subgenre, were of little use to the (future) practitioner. Instead, they highlighted the near infinite multitude of phenomena that Nature could bring forth. They satisfied the reader’s curiosity and offered physicians a welcome opportunity to show their ability to explain the seemingly miraculous and supernatural as in line with the laws of nature.