In 1927, Dr. Francis W. O’Connor arrived in Puerto Rico to teach at the then recently-inaugurated University of Puerto Rico School of Tropical Medicine. Over the course of three weeks, he delivered a series of lectures on filariasis, launched a research project, and met people of the diverse strata of the Island’s population. Faced with a full schedule, aimed to familiarize him with the health conditions of Puerto Rico, O’Connor immersed himself with considerable verve and interest. He would visit and comment about the fledgling health system, meet with residents of the leper colony, treat patients in the hinterlands, and examine the etiology of several tropical ailments. Combining the clinical eye of an experienced diagnostician with the visual flair of a watercolorist, O’Connor wrote a daily account of his activities. This book includes an annotated edition of O’Connor’s Diary of a Porto Rican Trip with a selection of photographs and five essays that expand on the diary’s historical, literary, and scientific significance.