Following experimental infectious bursal disease virus infections in four-weekold broiler chicks, turkey poults and ducklings, blood samples were chronologically collected and analyzed for postinfection (pi) changes. Although there was a net increase in packed cell volume values in chicks reaching a peak of 31% from 12 h to 144 h pi, there was, on the contrary, a general decline in the values in turkey poults and ducklings to minima of 26.5% at 12 h pi and 28.2% at 48 h pi, respectively. Leukocyte counts in chicks significantly increased (p < 0.05) to a peak of 66.83 x 103/μl at 120 h, while counts in poults decreased to a minimum of 26.75 x 103/μl at 96 h pi. Lymphocyte counts in chicks were reduced to a minimum of 5.9 x 103/μl at 48 h pi after an initial reduction between three and six hours postinfection. A similar decline occurred in poults with a minimum of 7.81 x 103/μl at 48 h pi. The trend of changes in heterophil counts for the three species was similar to those observed for leukocyte counts. While eosinophil counts in chicks initially increased to a peak of 1.93 x 103/μl at 6 h pi and subsequently declined, eosinophil values in poults declined to a minimum of 0.88 x 103/μl at 6 h pi, followed by an increase to a maximum of 5.7 x 103/μl at 72 h pi. However, all hematological values in ducklings remained relatively unchanged. These results showed that there was biphasic lymphopenia, eosinophilia and heterophilia in chicks, lymphopenia and delayed eosinophilia in poults, and relatively unchanged values in ducklings. This emphasizes the fact that different levels of susceptibility exist in the three poultry species studied.