Chicken embryo fibroblasts (CEF) infected with each of five stains of infectious bursal disease virus(IBDV) and control CEF were harvested and tested at various stages post-infection. Upon Agarose gel electrophoresis, DNA extracted from IBDV-infected and control CEFs exhibited a laddering Pattern. The amount of the DNA fragments was measared with enzyme-linked immunosorbent assay (ELISA). There was a significant increase in the amount of DNA fragments in each IBDV-infected group, as compared with the control group, and the amount of DNA fragmets showed some differences among the infected groups. These results demonstrated that the five IBDV strains all could induce apoptosis, but different IBDV strains exhibited variation in the capacity to induce apoptosis; quantitative change in apoptosis was better detected with ELISA.