The effects of the neem extract and azadirachtin on microorganisms in the rhizosphere were studied using mung bean as a model plant, because it is an economic plant and easy to cultivate, and any changes in the formation of root nodules by Rhizobium sp.can be easily observed. In a greenhouse, the mung beans were sown in one hundred and twenty 500-mL pots, half of which contained CS soil and the other half contained BS soil. Sixty pots were divided to five groups (twelve pots each). Then, once a week for a period of two months, the pots were treated with 50 mL of either neem extract or azadirachtin, at different concentrations as described above.