At the Austrian Ministry for Environment (now: Federal Ministry for agriculture and forestry, environment and water management) a working group was established to propose indoor air guideline values. This consists of representatives of different disciplines, such as physicians, toxicologists, engineers and lawyers. Already in the constituent meeting it was decided to employ a set pattern for establishing toxicologically sound guideline values. It was then agreed to use the pattern proposed by the German ad-hoc-working team. The interdisciplinary discussions, however, demonstrated the need for additional clarification, since representatives of different disciplines obviously interpret the various terms and principles differently. In particular, there is a need for discussing in detail the relation between the guideline values for indoor air to other air quality standards (outdoor air and workplace) and to specify their scope and application, especially the need to describe in greater detail what should be done in case either guideline value I or II was exceeded.