During the spring of 1983, fluid milk samples were collected from 359 bulk transporters representing 16 counties, municipalities and districts of Ontario, and were analyzed for organochlorine and organophosphorus insecticides plus selected halogenated industrial pollutants. Dieldrin, p,p′-DDE, heptachlor epoxide, and α-BHC were found in over 90% of samples, but none exceeded the accepted maximum residue limits. Polychlorinated biphenyls (PCB), lindane and pentachlorophenol (PCP) were found in 83, 68 and 57% of samples, respectively, with four samples exceeding the permissable PCB limit and one sample exceeding the permissable PCP limit. Residues of chlordane, endosulfan, p,p′-TDE, and p,p′-DDT were identified in only 1.9 to 4.7% of samples, and were present at levels only slightly above the detection limits. Hexachlorobenzene (HCB) was found at low levels in 40% of samples. Mean residues of organochlorines found were as follows (μg/kg butterfat): ∑DDT - 12; α-BHC - 5.3; lindane - 4.0; heptachlor epoxide - 3.9; dieldrin - 6.2; HCB - 0.67; PCB - 24; and PCP - 29. No residues of six organophosphorus insecticides, endrin, methoxychlor or mirex were detected in any samples. This survey was the sixth in a series beginning in 1967. Half-residue disappearance rates were calculated at 3.5, 5.4, 5.6 and 3.0 years for ∑DDT, dieldrin, PCB and HCB, respectively. A case history is included involving the misapplication of fenthion to a dairy herd which revealed a half-residue elimination from milk in approximately 3 d.