The effect of chronic consumption of metabisulphite, a food preservative, on the integrity of the rat kidney cellular system was investigated. The levels of activities of some 'marker' enzymes were measured both before and after administration of between 1 and 15 doses of the chemical compound. Feeding of metabisulphite (5 mg/kg body wt.) to rats resulted in loss of alkaline phosphatase activities from the kidney beginning after the first dose. This was accompanied by a reduction of lactate dehydrogenase activity which was noticed as a secondary reaction, taking place after five daily doses. This was accompanied by an increase in alkaline phosphatase and a decrease in lactate dehydrogenase activities in the serum. An increased urinary excretion of protein and alkaline phosphatase activity was also obtained. Other enzymes assayed (acid phosphatase and glutamate dehydrogenase activities) were not significantly affected in the tissues and urine. All these results indicated that there is cellular damage to rat kidney as a result of chronic consumption of metabisulphite. They also indicate that the damage was primarily on the plasma membrane. The proximity of the soluble portion of the cytoplasm to the plasma membrane also makes it a secondary site of injury in the kidney cell.