Recent advances in immobilized enzyme-based analytical methods, e.g., the cholinesterase-based water monitor 'CAM' (cholinesterase antagonsist monitor), have proved useful in the detection of organophosphate and carbamate pesticides. This work has now been extended to the detection of five high molecular weight chlorinated hydrocarbons at the parts-per-million (ppm) level in a water/methanol matrix. In the new method being developed, the lactate dehydrogenase (LDH) catalyzed reaction: pyruvate + NADH + H(+) yields (LDH) (inhibitor) lactate + NAD(+1) is used to detect the presence of chlorinated hydrocarbons, which reduce the rate of the reaction by inhibiting the enzyme. To date, the method has proved effective in detecting aldrin, toxaphene, Aroclor 1242, DDT, and pentachlorophenol. Nonchlorinated analogs, e.g. phenols, are detected only at orders of magnitude higher concentrations. The method has not yet been evaluated on environmental samples.