Clinical and hematological studies on 1 to 5-day old susceptible chicks inoculated intravenously with Avian Myeloblastosis Virus ( AM V ) are reported here. The onset of disease was seen 2 to 6 weeks postinoculation, the sick birds exhibiting extreme anaemia, accompanied by diarrhea and the appearance in the blood of numerous mysloblasts showing typical morphology. The blood plasma contained AMV.