During the summer of 1977 milk samples were collected from 308 bulk transporters picking up milk in the southern region of Ontario. These milk samples were subjected to a comprehensive analysis for organochlorine insecticides and selected halogenated industrial pollutants. Ninety-five percent of samples contained residues of p,p′-DDE, dieldrin, heptachlor epoxide and PCB, 68% contained residues of HCB, and 16% contained residues of p,p′-DDE and p,p′-TDE; chlordane and endosulfan were detected in only a few samples. Residues of aldrin, endrin, lindane, methoxychlor, mirex, PBB and chlorinated phenols were not detected. Mean residues of insecticides in milk fat were ∑DDT, 0.015 ppm; dieldrin, 0.011 ppm; heptachlor epoxide. 0.002 ppm; endosulfan, 0.001 ppm; and chlordane, <0.001 ppm. Mean residues of industrial pollutants in milk fat were 0.033 ppm PCB and 0.002 ppm HCB. Compared with a similar survey conducted in 1973 for an approximately identical geographical area, levels of ∑DDT, PCB, and HCB showed a significant decrease. dieldrin showed only a slight decrease and heptochlor epoxide and chlordane increased. Reports are presented on individual case histories involving the misapplication of endrin, lindane, and fenthion to dairy cattle. The rate of elimination of these compounds from milk is presented.