Although current guidelines target hospital employees who contact high-risk patients as a high priority for influenza immunization, there are few data to support or refute this recommendation. Therefore, the authors enrolled 179 hospital employees in a randomized double-blind placebo-controlled clinical trial during the 1985-1986 influenza season. Influenza immunization was performed without serious adverse reactions and there was no increase in absenteeism attributable to the vaccination. Among those who developed clinical influenza, there was a trend toward fewer days of illness in the vaccinated group compared with the placebo group (6.0 vs. 8.0, p = 0.07). There were no statistically significant differences between subjects receiving influenza vaccine and those receiving the placebo when comparing incidences of influenza-like illness, severities of illness, and sick absenteeism. Influenza immunization of hospital employees was performed at minimal cost and risk but provided little benefit, most likely because of an unexpected drift of the prevalent influenza strain away from the vaccine type.