Historians and archaeologists have extensively studied the history of health and illness in medieval England. Despite uncovering evidence of many diseases, especially fatal ones, questions remain about the impact of infirmity on people’s lives. How often were people unable to work because of illness? Were there seasonal patterns to such absences and did some people suffer recurring bouts of sickness? It has long been recognized that sick customary tenants could, in theory, be excused from performing their labor services (known as “works”) but few examples of this practice have been found. This article presents new evidence of infirmity on the manors of Ramsey Abbey. The monks excused sick tenants from performing their labor services for up to a year and a day, and sixty-two manorial accounts offer new insights into 229 cases of infirmity among their customary tenants in the fourteenth and early fifteenth centuries. These accounts reveal a variety of experiences, from acute illnesses that lasted just two days, to chronic and debilitating infirmities that could result in a year’s absence. Five weeks of autumn accounted for a high number of absences, perhaps reflecting the demands of the harvest, but also the possibility of workplace accidents or even fraudulent claims of infirmity.