Many human immunodeficiency virus (HIV)-infected patients suffer from impaired neurological function and dementia. This facet of the disease has been termed acquired immunodeficiency syndrome (AIDS)-associated dementia complex (ADC). Several cell types, including astrocytes and neurons, are not productively infected by virus but are involved in ADC pathophysiology. Previous studies of rat astrocytes showed that an HIV coat protein (gp120) accelerated astrocyte Na+/H+ exchange and that the resultant intracellular alkalinization activated a pH-sensitive K+ conductance. The present experiments were conducted to determine whether gp120 affected human astrocytes in the same fashion. It was found that primary human astrocytes express a pH-sensitive K+ conductance that was activated on intracellular alkalinization. Also, gp120 treatment of whole cell clamped human astrocytes activated this conductance specifically. Furthermore, gp120 inhibited glutamate uptake by primary human astrocytes. These altered physiological processes could contribute to pathophysiological changes in HIV-infected brains. Because the gp120-induced cell physiological changes were partially inhibited by dimethylamiloride (an inhibitor of Na+/H+ exchange), our findings suggest that modification of human astrocyte Na+/H+ exchange activity may provide a means of addressing some of the neurological complications of HIV infection.