We have studied the prevalance of extended spectrum beta lactamases (ESBL) in 250 fecal samples from 250 patients. Samples were straked onto Mac Conkey agar plates supplemented with ceftazidime (1 μg/ml) and ceftriaxone (1 μg/ml). Colonies were screened by the double-disc synergy test and combined disc test for ESBL production. Antimicrobial susceptibilities of ESBL producing isolates for various antibiotics were determined. All ESBL producing isolates were characterized by polymerase chain reaction (PCR). The rates of occurence of ESBL producing isolates among outpatients was 14% and among hospitalized patients was 22, 2%. ESBL producing bacteria were identified as Escherichia coli (76.3%), Klebsiella pneumoniae(18.4%), Klebsiella oxytoca (5.3%). The ESBL producing isolates recovered from our patients corresponded to a CTX-M type (89, 4%), SHV type (31.5%) and TEM type (76.3%). Fecal flora members producing GSBL may be a reservoir for ESBL genes and the information on the prevalence and types of ESBLs in human fecal flora may be very important to improve our understanding about the complex epidemiology of ESBLs.