The lead spreading from the industrial wastes and exhaust of the motor vehicles causes various health problems. The occurance of chronic and acute poisioning is observed as a consequence of lead exposure in industrial branches in urban life. Arginase which is thelast enzyme of the urea cycle is responsible for the detoxification of ammonia in mammals by hydrolysing arginine to ornithine and urea. Also the liver is the organ which has the highest arginase activity. The aim of this study was to find out some kinetic properties of rat liver arginase applied lead acetate. In this study, 28 Wistar albino male rats were used with the weight of 250±20 grams and approximately 8 weeks old, and divided 4 groups; Group-I: Control group,1 mL physiological-saline-solution/i.p, Group-II: Lead-acetate 25 mg/kg-i.p, Group-III: Lead-acetate 50 mg/kg-i.p, Group-IV: Lead-acetate 75 mg/kg ip. The lead-acetate was added into 1 mL physiological saline solution within 7 days, it was applied twice a day (morning-eveninig) intraperitoneally. At the end of the experiment, the rats in all groups were sacrificed by using the anesthesia and liver tissues were taken. The preincubation temperature for rat liver tissues was determined at 65°C and the preincubation time at 20 minutes, incubation time at 18 minutes and optimum pH at 10. It was observed that the enzyme showed the highest activity of 3 mM MnCI2 concentration. As a result, it was determined that Mn⁺² ions and preincubation at 65°C is required for the activation of the enzyme. It was observed that Km of the rat liver which was opposite to L-arginine of tissue arginase including leadacetate 50 mg/kg-i.p was aproximately 8.5 mM and control group was a proximately 11.5 mM. As a result, it was observed that decreasing Km and Vmax in the presence of Pb caused uncompetitive inhibition. Besides it was determined that when the amount of lead-acetate increased the arginase activity decreased.