Amp C type β-lactamases are commonly isolated from extended-spectrum cephalosporin-resistant Gram-negative bacteria. Amp C β-lactamases (also termed class C or group 1) are typically encoded on the chromosome of many Gram-negative bacteria. Differentiation of organisms expressing ESBLs from organisms expressing plasmid-mediated Amp C β-lactamases is necessary in order to address surveillance and epidemiology. Aim of the work:We are aiming at diagnosis of Ampc-β-lactamase producing Gram negative bacilli in nosocomial and community aquired infection by both phenotypic and genotypic methods. Diagnosis of Amp C β-Lactamases was done by Phenotypic and genotypic methods. Phenotypic identification was done using boronic acid, Cloxacillin and induction test and the genotypic identification was done using multiplex PCR. Our isolates were screened for Cefoxitin resistance .Thirty six out of 50 were positive Ampc by combined disc of Cefotetan and Boronic acid, 35 isolates out of 62 were positive for Boronic acid and cloxacillin synergy. Twenty two isolates out of 62 were positive for induction test. Sixteen isolates were confirmed as being plasmid-mediated Amp C β-lactamase producers by the multiplex PCR using family-specific primers.We conclude that for AmpC detection in E.coli, Klebsiella, Enterobacter the combined test method was considered the most reliable and easy to be available for the routine work followed by synergy by boronic then synergy by cloxacillin then the induction test. For detection of AmpC in Pseudomonas isolates the combined test was the best followed by synergy by cloxacillin then synergy by boronic then the induction test. Regarding Acinetobacter isolates, we found no significant difference between combined test, synergy by boronic, synergy by cloxacillin and induction test.