This study was performed to investigate the existence of bacterial etiology in development of ascites in broiler chickens. Samples of heart, lung, spleen and liver were collected from broiler chickens suffered from ascites (45 diseased and 52 freshly dead) for bacteriological and histopathological examinations from different farms at Ismailia province. The results showed that the overall incidence of bacterial isolation from ascitic birds were (55.67%) while, (44.33%) was negative for bacterial isolation. The most frequently isolated bacteria were Enterococcus spp.(52.5%),and E. coli (22.68%) besides Klebsiella pneumoniae 3.09%, Pseudomonas aeruginosa 1.09%, Citrobacter 4.12%.and Staphylococcus (6.18%). Enterococcus spp.was identified as Enterococcus faecalis, Enterococcus durans, Enterococcus hirae. Escherichia coli isolates were found serologically to be belong to 078, 0111 and untypable. Isolated Enterococcus spp. were highly sensitive to amoxicillin and sensitive to ciprofloxacin and enrofloxacin while they were resistant to Aminoglycoside (gentamycin and streptomycin), tetracycline and Chloramphenicol. Isolated E. coli was resistance to amoxicillin and erythromycin and sensitive to ciprofloxacin, enrofloxacin and gentamycin. Experimental infection of 18 day-old chickens inoculated intraabdominal and intratracheal with approximately  3 X 10⁷ CFU and 1.5 X 10^{7 (}Enterococcus faecalis, Enterococcus durans, Enterococcus hirae)and E. coli respectively in addition to,  another same inoculated groups and treated with susceptible antibiotics as combination of Ciprofloxacin and Amoxicillin in drinking water for five successive days post infection for enterococus spp groups and ciprofloxacin alone for E. coli infected group. Birds were monitored daily for clinical signs and mortalities .At necropsy a subjective scoring system was devised to quantify challenge effect by assigning each heart score of 1 to 4. the average of birds exhibiting ascites were 60%,40%,50% and 20% while mortalities were 60%,40%,50% and 50% as well as birds developing ventricular cavity were 80%,50%,40% and 10% for ⁽Enterococcus faecalis, Enterococcus durans, Enterococcus hirae)and  E. coli infected groups respectively. All infected and treated birds developed neither clinical signs nor mortalities. No clinical signs or gross lesions were demonstrated in control birds. Histopathological examination revealed epicardial fibrosis, hyaline degeneration of myocardial muscles, thickening of the fibrous tissue of the hepatic capsule, vacuolar degeneration and necrosis. The Lung showing serofibrinous exudates inside the alveoli and congestion of the blood vessels, desquamation of the epithelial cells of the bronchioles. No great differences was found in histopathological finding between naturally and experimentally infected birds  It could be concluded that bacterial agents have a considerable role in development of ascites in broiler chickens. It clearly refutes the postulation of complete exclusion of infectious agents as an etiology of ascites development in broilers