Low molecular weight dicarboxylic acids exhibit a semivolatile behavior and partition between gas and aerosol phases in the atmosphere. Here we present an approach for sample collection, which provides information about the gas/particle distribution of the investigated acids, but with less effort compared to commonly used denuder systems. The procedure was applied for the investigation of C2-C9 dicarboxylic acids at a continental background site in central Europe (Mt. Rax) and the urban site Vienna. The averaged gas phase contribution (n=12) determined for individual low molecular weight dicarboxylic acids varied between 4% (malonic acid) and 37% (glutaric acid) of the total collected amounts. Using the observed gas/particle distributions effective Henry's law constants were estimated. Between the carbon chain length of the investigated dicarboxylic acids and the magnitude of K-H* a dependence was observed-showing higher values for C2/C3 dicarboxylic acids (averaged 1.1x10(13) mol L-1 atm(-1)) and lower values for C4/C5 compounds (averaged 1.6x10(12) mol L-1 atm(-1)). (C) 2004 Elsevier Ltd. All rights reserved.