The activity of urinary enzymes of workers exposed to phenol from one to more than ten years was investigated. Both the urinary phenol levels and the activity of gamma glutamyltrans- ferase

lactate dehydrogenase. leucinearylamidase. alkaline phosphatase and lysozyme were markedly increased in comparison with that of the control group.The incremental activity of alkaline phosphatase was confined to male urine only. In the meantime

the activities of the corresponding serum enzymes were remaining low. It is evident that the serum enzymes were not the main source of their respective urinary enzymes and the lysozymes of the tubular epithelium of the kidney were the source of various enzymes. It is suggested that the estimation of the urinary enzyme activity could be of value as an early indication of renal damage in workers with phenol absorption