Mutant strains of bacteria were isolated through consecutive exposure to elevated concentration of endosulfan under carbon free media. The results showed that the most tolerant bacteria were Bacillus sp. The comparative degradation of endosulfan by mutant and their wild types was studied under soil conditions. Results showed that wild types (present in large number) showed faster decrease in half lives compared to the mutant strains (few in numbers). However mutant strains might have greater potential if they find a chance to propagate in massive numbers.