A total of 115 diseased and freshly dead broilers and broiler breeders' chickens were collected from different farms at different ages. They were suffering from respiratory signs and facial swelling. Complete clinical and postmortem examinations were recorded. Samples from lung, heart, trachea and air sacs were collected for bacteriological isolation. Antibiotic sensitivity test as well as experimental infection were applied. The results showed that 27 out of 115 (23.47%) were positive for isolation of O. rhinotracheale (16/64 from broilers 25% and 11/51 from broiler breeders 21.56 %). Experimental infection of 4 weeks old chickens via intravenous, intra-tracheal and intra-air-sac leads to decrease in feed intake and growth retardation (The mean of body weight in all infected groups were significantly (P < 0.05) lower than control group, depression, ruffling difficult breathing, conjunctivitis, sneezing, nasal discharge followed by facial edema. Postmortem lesions varied in severity according to inoculated routes and generally were tracheitis, arisaculitis, pneumonia, pericarditis, and perihepatitis, caseated material in air sac of some birds and arthritis. O. rhinotracheale   could be reisiolated from affected organs of experimentally infected birds. Mortality was recorded in two birds only (13.33%) after intravenous inoculation. The isolated O. rhinotracheale were sensitive to amoxicillin, ceftiofur colstin sulphate, erythromycin and tetracycline while were resistant to gentamycin, enrofloxacin, ciprofloxacin and trimethoprim.