Human neuroblastoma (IMR-32) cells were infected with herpes simplex virus type 2 (HSV-2) at a multiplicity of infection (MOI) of 2 plaque-forming units (PFU)/cell and were cultured at 40 degrees C for 14 days. Then neither infectious virus particles nor virus capsids were detected in these cells whereas the presence of virus-specific antigens was observed by immunofluorescent antibody staining technique in 16.9 +/- 3.2 per cent of the infected cell population. When the cultivation temperature was shifted down from 40 degrees C to 35 degrees C, reactivation of virus growth occurred after lag periods of 2-9 days. These findings indicate that the IMR-32 cells can be latently infected with HSV-2 at 40 degrees C and that virus growth may be inhibited at the level of synthesis of virus-specific macromolecules or at some step preceding nucleocapsid formation.