In this study the behaviour of the trace components caesium (Cs) and strontium (Sr) in a fluidized bed municipal waste incineration is investigated. Doped RDF (refuse derived fuel) was combusted and bed and fly ash concentration were measured for varied fuel injection temperatures and doping amounts. The distribution of the trace components was calculated and shows that Cs is mostly transferred to the fly ash fraction. The same was found to a lesser extend for Sr. The influence of both, injection temperature and doping amounts, was mostly inconclusive. The comparison of the distribution with data from grate combustion experiments shows a significantly higher transfer of Cs to the fly ash. This was even more pronounced for Sr and indicates a transfer of Sr mostly by entrainment of coarse particles in the flue gas. The experimental results give an indication for the release behaviour of Cs and Sr in fluidized bed municipal waste incineration and relevant influencing factors.