Factors that may influence the acceptance of influenza vaccination by health care workers were examined. The records of all employees at the University of Iowa Hospitals and Clinics were reviewed to identify those who received influenza vaccination in the 1991/1992 and 1992/1993 influenza seasons. Sex, age, race, marital status, occupational group, duration of employment at the centers, contact with patients, previous absenteeism, and annual salary of the employees who received the vaccine in the 1991/1992 influenza season were examined as possible factors that could be used to predict accepting the vaccine using logistic regression techniques. The logistic model that was developed was evaluated by applying it to the vaccination data for the 1992/1993 to test the goodness of fit. In the 1991/1992 season, 2,364 of 7,320 employees received the vaccine, representing an acceptance rate of 32%. During the 1992/1993 influenza season, 2,679 of 8,632 employees received the vaccine, representing an acceptance rate of 31%. Age, race, occupation, salary, and duration of employment were significantly associated with vaccine acceptance by all employees. Among nurses, older age, longer duration of employment, and previous absenteeism were significant predictors of vaccine acceptance. Among physicians, only duration of employment was significantly associated with vaccine acceptance. Among professional support personnel, female sex, being married, previous absenteeism, length of employment, higher socioeconomic status, and patient contact were significantly associated with vaccine acceptance. Among nonprofesional support staff, only older age was significantly associated with vaccine acceptance. When applied to the 1992/1993 vaccination data, the 1991/1992 model showed good agreement with the data. The authors conclude that older age, higher socioeconomic status, and longer duration of employment are factors predictive of influenza vaccine acceptance by health care workers. Sex, marital status, and previous work absenteeism are also important predictors of vaccine acceptance in specific groups of health care workers.