A total of 94 clinical isolates were collected from Gazi University Hospital, Turkey. Presence of ESBL positivity was detected using the double disk synergy test (DDST). ESBL isolates were further typed for the bla(TEM), bla(SHV), bla(CTX-M) and bla(OXA) using designed primers. ESBLs were found in 65 (69.14%) isolates using DDST. Plasmid DNAs of potentially ESBL positive strains were isolated. About 7.69% of the ESBL positive isolates did not harbour plasmid DNA. According to the PCR technique, only 2 additional isolates were found to be ESBL producers. blaTEM was the commonest genotype (73.43%), followed by blaSHV (21.87%) and blaCTX-M (17.18%), either alone or in combination. ESBL positive strains of Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii and Pseudomonas aeruginosa are increasingly found in hospital isolates. Because these strains become resistant to available antibiotics and they can pass the gene to other clinical strains, the quick detection of these strains in clinical laboratories is very important.