A series of laboratory experiments were conducted to find out the optimal conditions for the assay of urease activity in two different soils, viz., organic matter rich (S1) and organic matter poor (S2). The optimal conditions for the assay of urease activity were found to be 0.05M THAM buffer at pH 9.0 temperature of incubation 37ºC, time of incubation 2 hours and 5g of soil (S1 or S2). Effect of various factors affecting urease activity in S and S under optimal conditions was observed. A direct relationship between amount of carbohydrates added to both the soils and urease activity and a negative correlation between heavy metal (Ag-1, Hg-2, Co-1, Ni-2, Pb-2, Fe-3, Cr-3 and Cu-2) and soil urease activity was noted. Moreover, urease activity was always found to be more promising in soil from cultivated areas (organic matter rich) than from non-cultivated areas (organic matter poor).