พeported that the effect of sludge borne metals on enzyme activities is very complex and is due to: (1) the metal reacting with sulphydral groups of enzymes causing inhibition or inactivation of the enzymatic activity; (2) metals indirectly affecting soil enzymatic activities by altering the microbial community which synthesizes enzymes; or (3) a combination of these factors. Assays of soil enzyme activity are important in estimating the effects of metal pollution on the soil environment.