In order to find “bio-indicators” for monitoring the spread of persistent environmental chemicals (in this case chlorinated hydrocarbons), several animal species were sampled in three areas with different types of contamination. The concentrations measured were related to the results obtained from grass root analyses as the basic data for the assessment of the respective environmental contamination 1. The organisms' suitability as indicative matrices for the chlorinated hydrocarbon burdens was investigated according to the following criteria: analytical detectability of the chemical concentrations (A), accumulation characteristics in relation to the grass roots (B), and indicative function reflecting parallel accumulation (C). An “ideal” matrix serving as a bio-indicator able to detect all apparent chlorinated hydrocarbons accordingly could not be found. Instead, an order of suitability oriented along the above criteria could be attained. Finally, the gauging of an indicator with respect to the three different areas of contamination seems to be within reach, although apparently the variety of chemical burden in the selected areas is not sufficiently significant for this aim.