Seven brewery workers developed asthmatic symptoms after using chloramine (chloramine-T) powder as a sterilising agent. They gave positive weal and flare reactions to skin-prick tests with solutions of chloramine at strengths that caused no reactions in unexposed controls. The symptoms did not recur once the men had been removed from areas in which chloramine was handled. As well as causing irritant effects, inhaling dry or liquid aerosols of chloramine may cause sensitisation, with workers being prone to allergic asthma on reexposure. In view of this, measures should be taken to ensure that chloramine is not inhaled.