The new guidelines for indoor air hygiene in school buildings are intended as a response to current requirements in school practice. The recommendations aim to help to avoid mistakes in modernising school buildings and to provide hygiene-specific support in planning of new school buildings. The guidelines are laid out as follows: (a) In the general section the targets of the guidelines and the target groups are addressed. The current indoor hygiene situation in German schools is described, followed by the parameters with regard to peripheral issues which will not be dealt with further; (b) Part A deals with the hygiene requirements in the practical running of schools. Besides general requirements for maintenance and operation the important issues of cleaning and ventilation are considered, as well as minor building works; (c) Part B provides an overview of important chemical and biological contaminants in schools; (d) Part C looks at building and air conditioning requirements. The important issues of acoustic requirements is also addressed; (e) Part D shows how to deal practically with problem cases and list case studies with 'typical' procedures; (f) Part E provides a brief overview of existing renovation guidelines.