A cross-sectional study has been carried out at The National Institutes of Health to examine the prevalence of laboratory animal allergy (LAA) in a population exposed to animals, and to compare the prevalence of general allergy in the exposed v a control group. A group of 289 workers with light-to-moderate exposure to animals, 260 with heavy exposure, and 242 control subjects were interviewed. A slightly greater prevalence of general allergy was found among those working with laboratory animals (39%), than in the control group (33.9%), but the difference was not statistically significant. The prevalence of LAA in the total exposed group was 23.9%. A history of atopic problems and history of allergy to domestic animals correlated significantly with LAA, as did the number of species of animals handled and the average number of hours per week exposed to laboratory animals, with evidence of dose-response relationships.