Laboratory studies of chemical biodegradation are generally conducted using synthetic media inoculated with sewage, natural water, soil or hydrosoil. They tend to focus, for example, on identification of intermediate metabolites and end products, determination of mineralization rates and other kinetic parameters, and evaluation of physicochemical factors affecting the rates. Results from such studies provide the bases for appraising chemical persistence in native environments. In view of the above, the objectives of the study were: (1) to measure biodegradation rates of nine chemicals in BOD dilution water, and (2) to compare the rates with those reported in literature for the same chemicals in five natural waters. The comparison allowed an assessment of the environmental relevance of rates measured using BOD dilution water.