From experimental evidence, it was concluded that existing rules for the calculation of the behaviour of fire-exposed composite beams and slabs often lead to conservative solutions. Furthermore, the range of common applications had grown beyond the limits of existing calculation rules. It was felt that existing rules lacked a fundamental basis, in order to optimally design and evaluate fire-exposed composite beams and slabs. Therefore, a research project was started in 1989, in which CTICM (F), TNO (NL) and ARBED (L), together with both Delft and Eindhoven Universities of Technology, shared numerical and experimental research activities with respect to the behaviour of fire-exposed composite beams and slabs. The project aimed at gaining more insight into the behaviour -failure mechanisms in particular- of fireexposed composite beams and slabs by means of the development of numerical models and their validation based upon a limited number of full-scale well-instrumented fire tests. The final goal of this research project was to establish simple calculation rules, which would allow for easy and fast assessment of the fire-behaviour of composite beams and slabs. The project was co-sponsored by the ECSC; the part on composite slabs was conducted in the Netherlands, the part on composite beams in France. In the paper, the results of the Dutch part of the research project are described. After a brief introduction, the experimental programme is outlined. A total of 21 full-scale fire tests was performed on unloaded as well as loaded test specimens. These experiments have successfully been modelled using a general purpose finite element programme, with some pilot extensions. With the numerical model, a parameter study was performed. The results of this study were translated into a proposal for new simple calculation rules.