A case is described of a saturation diver with no previous history of asthma who repeatedly developed work-related symptoms of asthma at pressure, which appear to be causally related to the use of dichlorophen as a disinfectant agent. Although challenge tests were negative, suggesting that dichlorophen may have been acting as an irritant rather than as a sensitizer, the symptoms were abolished by the use of an alternative disinfectant agent. The potential importance of this effect in a diver is discussed, and the case highlights the importance of the use of nontoxic agents in the diving environment.