Immunologic responses to inhaled egg protein in egg processing workers was studied. The subjects were 25 workers from a factory that processed eggs into powdered egg yolk or whole egg and liquid egg white. Procedures included an interview with a physician, physical examination, skin tests, measurement of peak expiratory flow rate (PEFR), and serologic testing. Asthmatic illness was classified in a worker if the physician suspected occupational asthma (OA) or non OA based on clinical interview and examination, if the subject demonstrated more than 20 percent variability in PEFR on at least 1 day, and if the worker had symptoms of respiratory disorders. The physician diagnosed unequivocal OA in four workers, and in five other workers OA or non OA was suspected. No significant respiratory symptoms were found in 16 workers. "Definite asthma" (DA) was established in five cases, four of which were diagnosed as OA cases. The mean maximum PEFR variability for the five asthma cases was 35.6 +/- 13.9 percent; for the 20 non asthmatic subjects the value was 10.5 +/- 10.8 percent. Epicutaneous reactivity to one or more of the egg allergens was detected in eight of 25 workers, five of whom had DA. Three of 20 workers without asthma had positive skin reactions to egg allergens. Serum specific immunoglobulin-E (IgE) radioallergosorbent test (RAST) was positive to one or more of the egg allergens in four workers. All RAST positive workers exhibited good IgE binding to factory whole egg, egg white, ovomucoid, and ovalbumin. The immunoglobulin-G responses to lysozyme, whole egg, and conalbumin were elevated in egg exposed workers. The authors conclude that inhalation exposure to egg protein can cause IgE mediated OA. Serial PEFR measurements, skin testing, and RAST are useful diagnostic methods for identifying workers with allergic sensitization to egg protein.