Eighty five E.coli isolates were isolated from 3-6 weeks old broiler chickens suspected to be suffering from colibacillosis, complicated CRD, diarrhea, arthritis, slow growth rate and high mortality up to 15% from the examined 300 broiler chickens from different flocks. 250 (83.33%) were infected with E.Coli and all flocks were (100%) positive for colibacillosis where 85 E.coli isolates were obtained from which, only 42 isolate were sero-grouped into O55 (5.88%), O26 (8.23%), O111 (3.52%), O128 (14.11%), O125 (2.35%), O86 (8.23%), O126 (7.05%) while 43 isolates cannot be sero-grouped according to the available antisera. The invitro sensitivity of the isolated strains to various chemotherapeutic agents revealed that all strains were sensitive to Kanamycin and Amoxacillin (100%). All strains were resistant to Trimethoprim. In vitro pathogenicity testing of the isolated E.coli using Congo red medium revealed that all isolated strains were pathogenic (Congo red positive)