This paper reports on the annual variation of the composition of waste fuels fed to two different Waste to Energy (WtE) plants in Sweden. Twelve waste fuel samples from one year of sampling in each plant were analysed with Ion Chromatography and Inductively Coupled Plasma-Optical Emission Spectroscopy to study the variation of elements within and between the fuels of the two different plants and also to investigate any seasonal variations. The ultimate analyses show that the composition was rather similar throughout the sampling period for both plants, respectively. However, there was a larger variation in the content of ash forming elements within and between the plants. Trace metals, present in low concentrations, showed the widest relative variation. The samples were also analysed for dioxin and PCB content. The reported average value for all samples is 29 ± 15 ng I-TEQ dioxin per kilo dry waste. The calculated toxicity of twelve PCB congeners, reported as WHO-PCB, is less or close to the detection limit < 0.02 μg PCB WHO-TEQ per kilo dry waste.