As a part of the IEA Bioenergy, Task X-Conversion, Combustion activity, an international round robin test of a wood stove supplied with a catalytic afterburner (JØTUL 3TDCI-2) has been performed to investigate and compare the emission level of CO, particles/tar, hydrocarbons and NOx. The participating countries were Austria, Canada, Denmark, Finland, the Netherlands, Norway, Sweden. U.K. and U.S.A. The wood stove was tested according to national standards and test procedures. In addition, a comparison of the calculation procedures used to convert measured transient volumetric emission levels into average emission levels in g/kg dry fuel was performed, based on both arithmetic and weighted averaging. The results uncovered significant differences in ways of doing environmental evaluation. Particle emission measurements were found to be the best method to evaluate the environmental acceptability of the tested stove, since the particle emission level was least dependent of the national standards, test procedures and calculation procedures used. Finally, transient particle emission measurements are presented, which reveal a close relationship between particle and hydrocarbon emissions.