Background and Objective: To evaluate extended spectrum betalactamase (ESBL) positive strains of Klebsiella pneumonia and Escherichia coli in positive bacterial cultures. Materials and Methods: In this analytical cross-sectional study, between March 2006 and March 2007, 170 bacterial isolates including 133 cases of E. coli and 37cases of K. pneumonia were examined. All cases underwent double disk diffusion for ESBL. Demographic data were assessed and all data analyzed accordingly. Results: Patients’ mean age was 55±26.63 yr. Ninety six cases (56.5%) were female and 74 cases (43.5%) were male. Clinical presentation of infection were 118 cases UTI (96.4%), 15 cases septicemia (8.8%), 16cases wound infection (9.4%), 7 cases pneumonia (4.1%), 1 case meningitis (0.6%) and 13 cases other presentations (7.6%). Frequency of ESBL positive in E. coli isolates was 38 cases (28.6%) and in K. pneumonia isolates was 10 cases (27%). There was no significant correlation between ESBL positivity and age, gender, ward or clinical presentation of infection. Conclusion: Incidence of ESBL positive isolates of E. coli and K. pneumonia was high. These results should be considered in administration of broad-spectrum antibiotics by clinicians.