Catfish herpesviruses (Ictalurid herpesvirus-1 (IcHV-1)) belonging to the family Alloherpesviridae cause significant mortalities in catfish fry and fingerlings. Channel catfish virus (CCV) causes acute hemorrhagic infection in catfish during the hatchery and nursery phases of catfish culture. Blue catfish alloherpesvirus (BCAHV) is a strain of IcHV-1 isolated from blue catfish fingerlings in 1998. These herpesviruses are reported to be genetically similar (94%). Differential pathogenicity of these two viruses in terms of clinical signs, cytopathic effects (CPEs) in host cell cultures, histopathology, and percentage mortality in different catfish types were studied. Channel, hybrid, and blue catfish fingerlings were experimentally infected with BCAHV and CCV (10 3.5 TCID50 /mL) via immersion . Clinical signs of infection were comparable and included exophthalmia (popeye) and fluid-filled peritoneal cavity (dropsy). The CPE s produced by the two viruses in channel catfish ovary (CCO) cells followed similar morphological alterations (Figure 1) . Close resemblance in the clinical signs and CPEs caused by the viruses can be attributed to their genetic similarity. However, the susceptibility of catfish types varied with the virus strain . CCV caused significant mortalities in c hannel catfish fingerlings followed by hybrid and blue catfish. On the contrary, BCAHV was particularly pathogenic to blue catfish fingerlings and less virulent in channel catfish. Fish less than four months were severely infected by these viruses. The differential pathogenicity of CCV and BCAHV to multiple catfish types demonstrate the host-specificity of herpesviruses.