A community outbreak of measles prompted a serologic survey of personnel in a hospital serving that community. Two hundred sixty-six personnel, primarily physicians (129) and nurses (100), voluntarily participated. Serum specimens were initially tested by the immunofluorescent antibody and enzyme-linked immunosorbent assay (EIA) methods. Specimens with negative results by either test were further examined using the hemagglutination inhibition and plaque neutralization (PN) methods. If EIA and PN results were negative, an individual was considered susceptible. Only one of the 98 participants born during or after 1957 and none of the 168 participants born before 1957 were serosusceptible. The low rate of serosusceptibility, in contrast to previous studies of young adults, appears attributable to the sensitivity of the testing methods used. Based on our experience, institutions considering a measles serologic testing and immunization program should expect to identify very few serosusceptible personnel, even among those born during or after 1957.