We investigated the effect of glutathione on the replication of human immunodeficiency virus (HIV) in chronically infected macrophages, a known reservoir of the virus in the body. We found that exogenous GSH strongly suppresses the production of p24(gag) protein as well as the virus infectivity. This is related to a dramatic decrease in both budding and release of virus particles from chronically infected cells (either macrophages or lymphocytes), together with a selective decrease in the expression of gp120, the major envelope glycoprotein, rich in intrachain disulfide bonds and thus potentially sensitive to the effect of a reducing agent such as GSH. Overall data suggest that GSH can interfere with late stages of virus replication. This would be in agreement with data obtained in cells exposed to herpesvirus type 1 (a DNA virus) or to Sendai (an RNA virus), showing that the suppression of virus replication by GSH is related to the selective inhibition of envelope glycoproteins. These results suggest a potential role of GSH in combination with other antivirals in the treatment of virus-related diseases.