Cells were enucleated with cytochalasin B after infection with herpes simplex virus 1. When protein synthesis was blocked by cycloheximide from the time of infection, mRNA for viral alpha-infected cell polypeptides (ICP) 4, 0, and 27 accumulated in the cytoplasm and was expressed after the removal of both drug and nucleus. A host protein, ICP 22, whose synthesis is stimulated in intact cells, was not made, and viral protein ICP4, which is normally modified to a form that migrates more slowly in polyacrylamide gels, was not modified in the absence of the nucleus. After enucleation at 2 h postinfection, a number of viral beta and gamma proteins continued to be made, starting at 20 to 25% of the normal rates and declining with a half-time of about 2 h. The synthesis of ICP 4 declined more rapidly, suggesting that it is switched off in the cytoplasm.