Changes in spontaneous, amphetamine (AMP) and apomorphine (APO) induced locomotor activity were used to assess the effects of central nervous system (CNS) infection with herpes type 1 virus. A dual herpesvirus inoculation procedure was used in which the animals received an immunizing footpad inoculation followed at 2 weeks by an identical intracerebral challenge. Four weeks later the animals were tested with intraperitoneal injections of saline or d-l-amphatmine (0.5 and 2.0 mg/kg). When footpad herpes-virus was given via one or two injections, it had no effect on spontaneous or AMP induced activity. When food-pad-intracerebral herpes mice were tested 28-33 days post intracerebral inoculation, they demonstrated depressed AMP-induced but not spontaneous activity. AMP at a dosage of 5.0 mg/kg overcame the herpesvirus blockage of 0.5 and 2.0 mg/kg AMP induced activity. Intraperitoneal injection of APO in day 3 post-IC animals produced less suppression of activity in the virus group than in the controls. These results suggest that non-fatal CNS herpes infection produces hypoactivity, in contrast to thehyperactivity during acute fatal CNS herpes encephalitis (Lycke & Roos, 1975), and that the effect may be due to alterations in postsynaptic receptor sensitivity.