Mouse hybridoma clones were examined for their ability to support replication of herpes simplex virus (HSV). Infection of hybridoma clone 1 cells producing an antibody not specific for HSV resulted in a persistent infection with a continuous production of infectious virus, whereas infection of the parental myeloma cells X63-Ag8.653 led to an abundant virus production and extinction of the culture. In contrast, infection of hybridoma cells producing HSV-specific antibodies was restricted to a few weeks. Infectious virus was isolated for a maximum of 10 days and, afterwards, viral antigens were detected by immunofluorescence for a maximum of 18 days. The neutralizing capacity of the antibodies was not essential since the pattern of infection in clone III E8 cells, producing a non-neutralizing antibody, did not differ from that observed in clones 2c and VI A6, which produced highly and weakly neutralizing antibodies, respectively. After loss of viral antigen, HSV DNA was no longer detected by Southern blot hybridization in hybridoma clone 2c cells. Since no difference other than the specificity of the produced antibodies is suspected between the hybridoma clones, the results suggest that the presence of HSV-specific antibodies in the B-lymphoid cell cultures is responsible for virus elimination from the cells.