The aim of this study was to determine the antibiotic susceptibilities of Escherichia coli strains producing extended spectrum beta-lactamases (ESBL) isolated from various clinical samples of inpatients in the Clinics of Cebeci Campus, Medical School , Ankara University. The positivity of ESBL was determined by modified double disc synergy test (MDDST). It was found out that imipenem (98% senstivity) was the most effective antibiotic and ticarcillin/clavulanic acid (84% resistance) was the least effective. The susceptibility rates of meropenem, piperacillin/tazobactam ,amikacin, cefoxitin, netilmicin, quinolons and gentamicin, cefepim, tobramicin, trimetoprim/sulphametaxazole, tetracyclin were 96%, 86%, 84%, 72%, 48%, 32%, 30%, 20%, 14%, 12%, respectively. All strains were susceptible to colistin.