Ascites syndrome is an abnormal increase of non-inflammatory transudate in one or more of the peritoneal cavities or potential spaces. Ascites syndrome is considered as a main problem in broiler raising industry. Hypoxia is the factor for increase pulmonary blood pressure because of ascites syndrome in broilers. In this study, 120 pieces Ross variety broilers and 120 pieces Arbor-acres broilers were divided into two groups involving three with forty parts repetition. Raising conditions such as temperature, hum density, nutrition, vaccination and water were the same. In order to increase sensitivity broilers to ascites syndrome, pellet and cold stress were applied. For doing so, from 7 un days 16ºc was applied, then temperature reached to 22ºc and fixed until raising period. Ascites syndrome incidence rate in Arbor-acres chicks was more than Ross chicks. Hematocrite parameter was increased in Arbor-acres chicks from third weeks relative to Ross broilers it is meaningful in 35th day (p