In chickens, CAV appears to replicate primarily in haemopoietic precursor cells in the bone marrow and in thymic precursor cells in the thymus cortex where it has been shown to cause cytolytic infection. This work was carried out on ninety healthy one-day-old chicks of Egyptian breed. These chicks were classified into three equal groups (I , II, and III) Sacrificed after one, two and three weeks respectively. Each group was subdivided into three equal subgroups, representing the control, reference and field subgroups, inoculated intraperitoneally with saline, reference strain virus and field strain virus, respectively. The obtained results showed significant decrease in erythrocytic counts, haemoglobin concentration (in groups II and III) and PCV (in all groups) in both reference and field subgroups. It was noticed that there was a decrease in weight of some lymphatic organs like thymus and bursa fabricious in relation to body weight, and this means that the virus has immunosupressive effect. The biochemical tests on serum of both field and reference strain exhibited significant decrease, in serum iron (in all groups), serum total proteins and albumin (in group III only) and in serum globulins in both first and second groups. On the opposite side, both reference and fiel subgroups revealed significant increase in serum urea in groups II and III), serum creatinine and serum alkaline phosphatase in all groups and serum alanine aminotransferase (ALT) in group III only. Furthermore, serum total and indirect bilirubin showed significant increase only in field subgroup of group I and in both reference and field subgroups of group II and III. Meanwhile, serum inorganic phosphorus, phospholipids and direct bilirubin revealed non sgnificant changes. From this study, It was concluded that the d picture which appeared as a decrease in erythrocytic count & Hb concentration & decrease in haematocrit below 25 and the increase in liver function enzymes can be used as laboratory tests in CAV diagnosis in addition to symptoms of disease & histopathological examination and both virological and immunological tests.