We conducted allergy skin-prick testing on 207 young cereal grain workers within 0.27 years of the commencement of their employment in the grain industry and again after 1.34 years of employment on 124 workers. We also studied 120 control subjects on the first observation and 105 on the second observation. Grain workers had lower prevalence than did the controls of positive skin tests on the first observation, and this difference increased by the second observation. Respiratory symptoms were more frequent among grain workers with positive skin tests who dropped out of the industry than among those who stayed in the industry. We conclude that atopic status may be a factor in job selection and drop out decision making and may be a factor explaining the healthy worker effect.