The disinfection of operating theatres and adjoining areas is carried out with chemical disinfectants containing not only formaldehyde but also glutardialdehyde. The cleaning staff is therefore unavoidably exposed to these two substances. Adequate and correct evaluation of staff exposure must be based on exact quantification of these aldehydes in room air. The statutory MAK-levels of 0.5 ppm (formaldehyde) and 0.2 ppm (glutardialdehyde) call for highly sensitive and specific analytical methods for monitoring exposure that should be suited for personal measuring as well. Since previous methods have failed to meet these requirements, we have adapted a newly developed method for the specific measurement of formaldehyde and other aldehydes and ketones for the personal monitoring of formaldehyde and glutardialdehyde. Detailed personal measurings over whole shifts and of short-term peaks have yielded the following results: During routine disinfection activities in operating theatres using low concentrations of disinfectants, the limits prescribed by MAK can be respected. Disinfections to prevent notifiable infectious diseases in accordance with the Federal Epidemic Law (Bundesseuchengesetz) involving the use of higher disinfectant concentrations are liable to exceed the MAK limits for formaldehyde and glutardialdehyde. If for reasons of hygiene this excess exposure cannot be avoided, effective protection of the cleaning staff from unacceptably high concentrations of these substances can be ensured only by providing personal protective outfits.