We examined the peripheral nervous system (PNS) (nerve conduction velocity (NCV)) and the central nervous system (CNS) (basal ganglia-mediated psychomotor speed) in 93 males seropositive for human immunodeficiency virus type 1 (HIV-1) with no prior history of opportunistic brain disease, antiretroviral treatment or intravenous drug use. Patients with different degrees of slowing of peroneal and sural NCV showed no significant differences in psychomotor speed as assessed by tremor peak frequency, most rapid alternating movements, reaction times and contraction times. There was no significant correlation between psychomotor measures and NCV. Psychomotor slowing test findings were independent from peripheral nervous system damage indicating uncorrelated disturbances of CNS and PNS function in HIV-1 infection. Differences in HIV-1 viral quasispecies or host responses may determine the predominance of CNS or PNS injury.