Soil biomass is supposed to support phenomena which is usually occurred in pH close to neutral condition and at a temperature range between 20 to 40 ° C . The nature of the process is so that they cannot be undertaken without an enzyme-catalyzed reaction. Enzymes are proteins which are responsible for catalyzing biological processes. The enzymes possess different degrees of specificity and high catalytic rates. Ureases are widely distributed in nature and catalysis the hydrolysis of urea to ammonia and water. Soil microbial and enzymatic activities are known to be responsive to environmental stresses including drought and trace metal. The objectives of this study were to: 1-fractionate soil urease to two distinct pools of intra- and extracellular and 2- assess their response to drought and Cd stresses. Two separate researches were conducted. In the first one, nine surface (0-15 cm) calcareous soil samples were collected from western part of Isfahan province, the soils were all under small grains. The fractionation of the urease activity was performed by means of two techniques a) microwave irradiation and b) chloroform fumigation. In the second research the surface soil (0-15 cm) of two adjacent counterparts of natural oak forest and deforested areas were sampled. The intra- and extracellular activities of the soil urease were separately measured using chloroform-fumigation and their responses to drought and Cd stresses were assessed. For drought stress, soils were incubated at 25 °C for 60 days at 10 and 50 % water holding capacity. Another moisture treatment was also run in which the moisture content decreased from 50 to 10 % gradually during the same period of time. In a parallel experiment soils were treated with 5 µmol g -1 of Cd. A control treatment without application of Cd was also considered. At the end of either drought or Cd stress application, two fractions of urease activity were measured. Analysis of variance and mean separation were performed using a completely randomized design with a factorial arrangement. In case of paired comparison paired t -test was used. Results of the first experiment indicated that extracellular fraction of the urease were not correlated neither with the total nor the intracellular activities. Regardless of the technique used (microwave irradiation or chloroform fumigation) the result were similar. It was also observed that regardless of the technique, intracellular and total urease activity were significantly (r = 0.99, P 0.01) associated. However, the absolute values obtained from chloroform-fumigation technique were considerably greater than those obtained by microwave-irradiation, revealing that microwave irradiation have presumably negatively impacted some parts of extracellular urease activity as well as its intracellular fraction. Results of the second research indicated that Cd inhibited extracellular activity of urease. The degree of inhibition was greater in the forest than that of the deforested counterpart. Surprisingly, intracellular urease activity was slightly increased. No statistical interaction was observed between fumigation and Cd stress. Drought stress decreased the level of extracellular urease activity and the rate of decrease was greater in the forest compared to the deforested counterpart. Total activity was slightly increased in the drought stressed soils. Intracellular urease activity was increased under 10% water holding capacity while it was decrease when the soil experienced a water cycle between 10 to 50%. No statistical interaction was observed between fumigation and water stress. Overall, we conclude that chloroform fumigation is much more reliable than microwave irradiation for fractionation of soil urease activity. Intracellular activity was the major fraction of the total urease activity in the soils studied. Soil management history controls the degree of inhibition of soil urease under stress condition. Keywords : Urease, Microwave irradiation, Chloroform fumigation, Intracellular activity, Extracellular activity, Cadmium, Drought stress.