This study was carried out on 68 buffalo-calves aged from 2-8 month from a private farm in Dakahlia Governorate .Diseased calves were suffering from severe dyspnoea, cough, nasal discharge, pyrexia and abnormal lung sounds. Bacteriological examination of 98 samples (20 clinically healthy, 38 clinically diseased and 40 samples from each the nose, trachea, lung and lymph nodes of 10 freshly dead and emergency slaughtered calves) revealed that 83 (84.7%) samples from clinically healthy calves, diseased and freshly dead and emergency slaughtered calves were positive for bacterial infection where 49(59.0%) were as a single infection identified as Pasteurella multocida21(42.9%), E.coli 11(22.4%), Staph. aureus 8(16.3%), Streptococcus pneumoniae 3(6.1%) and P.haemolytica 6(12.2%)  ,however 34(41.0%) were mixed infection identified as E.coli with           P. multocida 17(50.0%), Staph.aureus 7(20.6%) and  Strept.pneumoniae 3(8.8%) as well as P. haemolytica with Staph.aureus 7(20.6%). Pathogenicity test for P. multocida isolates revealed that all injected mice were dead through 24-48 hours. The results of the antimicrobial sensitivity test showed that Enrofloxacin, Ceftiofur, Erythromycin and Florofenicol were the most effective antibiotics for treatment.