Almost 30% of the precious agricultural output of India is lost owing to pest infestation. In India. pesticide consumption for protecting crops is about 3% of the total world consumption. Monocrotophos (MCP), an organophosphorus insecticide, is widely used to control insects on crops. Being readily water soluble and highly toxic, its removal from wastewater generated during manufacture becomes inevitable. Bioremediation of wastewater containing MCP by Arthrobacter atrocyaneus, Bacillus megaterium, and Pseudomonas mendocina was highest at pH 8.0, but maximum reduction in Chemical Oxygen Demand (COD) was at pH 7.0. Removal of MCP and reduction in COD by B. megaterium and Ps. mendocina were highest at 35degreesC. while with A. atrocyaneus, it was maximum at 30degreesC, under aerated culture condition and inoculum density of 10(8) cells/ml. Use of pure cultures for bioremediation of effluent containing MCP appears to be the first such attempt.