Sixity sick pigeons of different ages and sources were collected from Assiut Governorate. 60 samples from crop, 60 samples from liver and 60 samples from intestine were taken for isolation of some gram positive organisms which can affect pigeons. After biochemical tests, this survey revealed the presence of Streptococcus bovis, Staph.aureus and Corynbacterium pyogenes at rates of: 25%, 12.7% and 5% respectively. Serotyping of isolated Streptococcus bovis revealed that it was biotype I, serotype 2. Experimental infection of 7 month old healthy pigeons with Streptococcus bovis intravenously showed septicaemia for 60% of birds through 3 days after infection and congestion of all carcasses, while the other 40% of birds revealed depression, loss of appetite, decrease of body weight, slimy green dropping. 2 weeks postinoculation the postmortem examination revealed pneumonia, airsacculitis, congestion of liver, spleen and kidneys, mottling of the pancereas with the presence of ulcer and gases in the intestine. While the orally infected pigeons showed the same previous lesions but after one month of infection, beside the presence of lamness and inability for flying. Reisolation of Streptococcus bovis from experimentally infected birds was succeeded. In vitro sensitivity test showed that ampicillin, enrofloxacin and erythromycin are the most effective drugs against Streptococcus bovis.