Objective: Extended spectrum beta lactamases (ESBLs) have been observed virtually in all the species belonging to the family of Enterobacteriaceae. The enzymes are predominantly plasmid mediated and are derived from broad-spectrum beta lactamase genes TEM, SHV, CTX-M. This study was undertaken to characterize ESBL producers in Trichy, Tamilnadu. Methods: Total of 361 blood samples were screened for ESBL producing isolates. The organisms isolated were subjected to morphological and biochemical test and the isolates identified were predominantly Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae. Antibiotic susceptibility test was performed employing Kirby Bauer's disc diffusion method. Results: PCR analysis for β-lactamases genes of the family TEM, SHV and CTX-M was carried out. Among the isolates obtained 138 ESBL positive for E. coli harbour 75% TEM gene, 66% SHV gene and 71% CTX-M gene, followed by K. pneumoniae, and E. cloacae. Conclusion: The results show an emergence of ESBL positive strains out of 361 isolates 250 samples were confirmed as ESBL producers.