A 26-year-old man employed in a company which manufactured hen egg white derived lysozyme for use in the pharmaceutical industry was evaluated for occupational asthma. The worker began to experience immediate-onset asthmatic symptoms two months after starting to work with egg lysozyme powder. The work process involved the production of approximately 1,000 kg of purified dried lysozyme powder per week. Prick skin testing was positive to egg lysozyme (50 mg/ml) and other egg protein components, but negative to whole egg white and egg yolk reagents. Serum specific IgE to egg lysozyme was documented. Decrements in serial peak expiratory flow rates were associated with lysozyme exposure at work. A specific bronchoprovocation challenge to lysozyme powder was positive demonstrating an isolated immediate asthmatic response (48 percent decrease from baseline FEV1). This is the first reported case of lysozyme-induced asthma specifically caused by inhalational exposure to egg lysozyme.