Residues of the most varied chemical substances can be found in milk and in milk products. For the transfer into milk such factors as fat solubility, persistance with respect to metabolic processes and accumulation capacity in certain organic systems are of particular importance. For the description of the situation with respect to residues of chlorinated insectides the results of analyses obtained in 20 supply areas of the German Federal Republic are presented and interpreted. In 1974 the following mean values were found (fat basis): alpha-HCH 0.04, gamma-HCH 0.072, heptachloro-epoxide 0.024, dieldrin 0.021 and DDT 0.20 ppm. These mean values are far below the max. quantities legally permissible and in no way constitute a toxicological risk (referred to ADI). In the German Federal Republic the concentrations of hexachlorobenzene in some cases reach the permissible max. quantity of 0.5 ppm on a fat basis. There is reason to assume that this substance finds its way into the milk not only via its application as a fungicide but probably also via a number of other, in part unknown, sources of contamination in or on vegetable products. With PCB (polychlorinated biphenyls) average concentrations from 0.2 to 0.3 ppm must be expected to be present in milk and milk products (fat basis). At present a toxicological interpretation of the values found is hardly possible.