The aim of this study was to establish the mean plasma GBV-C/hepatitis G virus (HGV) RNA load in groups of GBV-C/HGV-infected individuals with varied immune status and to determine the most frequent patterns of evolution of the plasma GBV-C/HGV RNA load over time during the natural history of infection. The mean plasma GBV-C/HGV RNA load observed was, from the lowest to the highest: 5.21 log in immunodepressed multiply-transfused patients, 6.45 log in HIV-positive individuals, 6.66 log in immunocompetent multiply-transfused patients, and 6.71 log in blood donors. The difference was significant between the four groups (P < 0.0001). The most frequent pattern of evolution of the plasma GBV-C/HGV RNA load was as follows: after the primary GBV-C/HGV infection, the viral load was elevated from the onset; then, a high, persistent and relatively steady viral RNA level was the rule; and when it occurred, the loss of viremia was not preceded by a decrease before recovery from GBV-C/HGV infection.