The kinetics of diazinon degradation in soils as affected by the presence of potentially toxic elements was studied. Metal (Zn2+, Cd2+, V3+ and Mn2+) treated soils as well as the control soils were spiked with diazinon at two concentrations of 10, and 50 mg kg-1. The residual diazinon concentrations were measured by corona discharge-ion mobility spectrometry at 0, 1, 10, 30, and 60 d. Degradation time (DT50) was calculated using three kinetic models. At 10 and 50 mg kg-1 of diazinon, no residual concentration could be detected at the day 30 and 60, respectively. In the Shervedan soil, the DT50 values for 10 and 50 mg kg-1 spiked diazinon concentration ranged from 0.51 to 2.3 d and 2.87 to 5.31 d, respectively. The greatest and the lowest DT50 values were consistently obtained in the control and V-treated soil. In the Lavark and Chamaseman soil, the pattern was similar to that of the Shervedan soil, except that Zn was more stimulatory than V in the Lavark soil. In general, metal-treated soils revealed lower diazinon concentrations. For the first time, it is reported that V can enhance the rate of diazinon degradation in soils. Overall, it is concluded that V and Zn are the most stimulatory potentially toxic elements for enhancing diazinon degradation in the soils. Therefore diazinon degradation time in the metal polluted soils is generally shorter.