a stunting syndrome was observed on most of broiler chicken farms located in Upper Egypt which was characterized by an unusual high incidence of visible unevenness in growth between 10-15 days old with maximum difference in size was seen at four weeks old. Different clinical and pathological features of the natural syndrome were described. Several reoviruses were isolated from gastrointestinal homogenate and visceral organs of severe clinically diseased broiler chicks. All reovirus isolates produced characteristic pocks on chorio-allantoic membrane (CAM) of embryonated chicken eggs (ECE) and mortalities between 3-7 days posinoculation (PI). All isolates were insensitive to chloroform treatment, did not hemagglutinate chicken erythrocytes and positive in agar gel precipitation (AGP) test against standard reference reovirus antiserum. Pathogenicity comparison between the six islated gastrointestinal reoviruses in ECE was carried out. Pathogenicity of gastrointestinal homogenate and reovirus isolated from the same field cases into 1-day-old broiler chicks was done. Clinical signs, pathological findings, mortalities in experimentally infected chicks and virus reisolation were reported.