Low-molecular weight dicarboxylic acids are important constituents ofthe organic fraction of atmospheric particulate matter in remote and polluted regions. The knowledge on their sources is sparse, however, and organic aerosols in general need to be better characterized. Observations of C2-C5 alpha,omega-dicarboxylic acids (DCAs oxalic, malonic, succinic, and glutaric acid) and C2 oxomonocarboxylic acid (glyoxylic acid) from rural and urban sites in different seasons in Germany are reported using filter sampling and ion chromatography. The C2-C5 DCAs accounted for (by average) 0.07-0.51 microg m(-3) at the various sites corresponding to 3.4-23 mg g(-1) of total suspended particulate matter and glyoxylic acid for < 0.18-0.28 mg g(-1). Both, the transport of air masses over the continent and the summer season favored the occurrence of the acids. Secondary photochemical formation dominated the sources. It was found that for central Europe the anthropogenic emissions are more important than the biogenic emissions for all the acids determined and most important for oxalic acid. The biogenic precursors play a signifcant role for malonic acid. The influence of the marine sources was detectable for malonic and glutaric acid.