Presence of Bush class C enzymes in uropathogenic strains of Klebsiella pneumoniae & E. coli resistant to extended spectrum cephalosporins is an emerging threat to clinical therapeutics. These resistant strains result in considerable treatment failure and cannot be detected by routine antibiotic sensitivity screening methods. An effort was therefore made to study AmpC beta lactamase production in E. coli and Klebsiella pneumoniae strains causing UTI. A total of 126 E. coli and 49 K. pneumnoniae strains isolated from urine samples were selected for study out of which AmpC beta lactamase production was seen in 23% E. coli (29 isolates) and 18% K. pneumoniae (49 isolates). The susceptibility of AmpC beta lactamase producers to Imipenem, Nitrofurantoin and Amikacin was found to be 100%, 92% and 80% respectively. Thereby the present study emphasizes the importance of monitoring and control of usage of extended spectrum cephalosporins.