(1) To merge Occupational Health (OH) and Human Resources (HR) administrative data to describe reasons for absenteeism among hospital employees and (2) to consider the advantages and disadvantages of using these combined data for surveillance of health care workers. This study utilized a retrospective cohort design, involving a record linkage of two administrative databases at a Canadian general hospital: OH and HR. Data were included for the period of June 1, 2004, to May 31, 2005. Data linkage was performed using sex, postal code, and date of birth. The most common self-reported reasons for absence were respiratory illness (31%), gastrointestinal illness (17%), and musculoskeletal injuries/disabilities (15%). Employees working in the Department of General Medicine experienced the highest number of times absent--1.9 per 1,000 work hours. The department with the highest percentage of staff not reporting to OH was General Medicine (43%). This research highlights the issue of absenteeism among health care workers and the need to improve reporting of illness and injury to OH for surveillance efficacy. Further, a public health surveillance system that monitors OH visits among health care workers can facilitate public health practice.