This research was carried out to isolate some soil microorganisms capable of degrading organophosphorus pesticides (diazinon and nemacur). Three isolates which confirmed in their abilities to degrade and utilize diazinon and nemacur as a sole source of carbon and nitrogen were identified as Bacillus polymyxa, Pseudomonas fluorescens and Streptomyces aureofaciens. Obtained data showed that diazinon and nemacur amounts decreased with elapsed time in inoculated medium. The rate of decrease in inoculated medium was faster than that in uninoculated one. Since, 22.71, 63.82, 62.60 and 47.51% of the added diazinon disappeared from the uninoculated, inoculated medium with Bacillus polymyxa, Pseudomonas fluorescens and Streptomyces aureofaciens, respectively throughout the first 15 days of diazinon addition. Whereas, the disappearance rate of nemacur at 15 days of incubation period were 4.8, 28.04, 28.30 and 12.11% for uninoculated, inoculated medium with Bacillus polymyxa, Pseudomonas fluorescens and Streptomyces aureofaciens, respectively. The compounds produced from the biodegradation of diazinon pesticide by various investigated microorganisms in this study are diazoxon, diethylphosphate, 2-isopropyl-4-methyl-6-hydroxypyrimidine, 2-hydroxy-l-methyl-6-methylpyrimidine and l,3-dimethyl-2-nitrobenzene. While, the compounds produced from the biodegradation of nemacur (fenamiphos) pesticide are fenamiphos phenol, fenamiphos sulfone and fenamiphos sulfoxide.