The content of polybrominated and mixed polyhalogenated dibenzo p-dioxins (PBDD and PXDD) and dibenzofurans (PBDF and PXDF) as well as of other polyhalogenated aromatic compounds in a series of samples of sewage sludges from municipal waste water treatment plants in the Federal Republic of Germany has been investigated. The analytical procedure developed for the determination of PCDD and PCDF in our laboratory was extended to the determination of PXDD and PXDF in this matrix. In all samples PCDD, PCDF, PCB, chlorobenzenes and octachlorothianthrene could be detected. Mono- to pentabrominated dibenzofurans (PBDF) and, compared with PBDF, relatively high levels of tri- to heptabrominated diphenylethers (PBDPE) were detected. Polybrominated dibenzo-p-dioxins, mixed polyhalogenated PXDD and PXDF, though present in automobile exhaust, and mixed polyhalogenated diphenylethers were not found in the sewage sludge samples. The fact that only Mono- to PentaBDF but relatively high concentrations of PBDPE were found in the samples, strongly suggests that the main source of PBDF in sewage sludge are brominated flame retardants.