Title: Detection of Metallo beta lactamases production in Gram Negative organisms by different phenotypic methods and their antimicrobial susceptibility pattern at a Tertiary care Hospital, Jaipur. Introduction: The production of metallo beta lactamases is an important mechanism responsible for the increased Carbapenem resistance. Carbapenems are often regarded as last resort antibiotics in the treatment of clinical conditions due to MDR organisms. Current study was done to detect the prevalence of MBL producing organism in this hospital and antimicrobial susceptibility pattern of MBL producing organisms. Material and Methods: This study was done on all clinical samples received in m Department of microbiology, National Institute of Medical Sciences and Research, Jaipur over a period of 6 months from June 2018 to November 2018. Samples were received and processed as per the standard guidelines and antimicrobial susceptibility testing was done according to the standard CLSI Guidelines. Detection of MBL production in Imipenem resistant strains was done by using Modified Hodge test, Double Disc synergy test, Disc Potentiation test and Thiol based compound test. Result: Out of the 584 Gram Negative isolates, 159 isolates were found to be resistant to Imipenem. Majority of the MBL producing organisms were found to be multidrug resistant organisms. Only Polymixin B and Colistin showed better sensitivity towards MBL producing isolates. DDST method showed better result as compared to other methods. Conclusion: MBL production in organisms is a leading cause of treatment failure as these enzymes inhibits the action of Carbapenems. High prevalence of MBL producing organisms is alarming sign and strict specific measures must be implemented to avoid the adverse outcomes