OBJECTIVES: The European Co-ordination on Diesel Soot Exposure (ECDSE) working group organised a laboratory inter-comparison which integrated both the sampling and the analytical determination. The aim was to gain more information on the performance of the methods for the determination of diesel particulate matter at workplaces and on their comparability, and to also confirm that the requirements of the European standard EN 482 are fulfilled for this analytical procedure. METHODS: Sampling was carried out in a diesel aerosol test chamber where participants used their own sampling devices. Overall, ten sampling exercises at two different concentration levels were performed and both personal air sampling systems and stationary samplers were used. The analytical determination was performed according to the laboratory's own standard procedure. RESULTS: There was good agreement between the laboratories for the determination of organic carbon (OC), elemental carbon (EC) and total carbon (TC). Almost all the results when expressed as a coefficient of variation were in the range +/-30% of the overall means. The results also showed that the coefficient of variation for OC was approximately twice the coefficient of variation for EC. This is not too critical, because existing occupational exposure levels (OELs) are based on the measurement of EC. CONCLUSIONS: The inter-comparison showed that existing analytical procedures for the determination of diesel particulate matter at workplaces fulfil the requirements of European standard EN 482. Both personal air samplers and stationary samplers give comparable results. The parameters for the analytical determination are not critical within the range of parameter values presented in this article. Additionally, it may be concluded that the diesel aerosol test chamber used in this exercise is well suited for producing an atmosphere containing a constant and reproducible level of diesel particulate matter.