The antimuscarinic compound atropine shows an antiherpesvirus effect as measured by the protection of the cell monolayer and the reduction of the formation of new infectious virus. Atropine at a concentration of 200 micrograms/ml blocks the production of new infectious herpes simplex virus-type 1 virions. At that concentration, it has almost no effect on cellular or viral protein synthesis even when atropine is present from the beginning of the infection. The glycosylation of viral proteins is almost totally blocked when atropine is added. Although the viral proteins are underglycosylated, the formation of new herpes simplex virus type 1 virions takes place. The virions formed in the presence of atropine are noninfectious, and their protein composition, as assessed by labeling with [35S]methionine, is similar to that of the control, except that they are not glycosylated.