Interleukin 10 is a pleiotropic cytokine that is overexpressed in HIV-infected patients. Here, we investigated IL-10 expression in primary cultures of monocyte-derived macrophages (MDMs) in response to in vitro infection by HIV-1/Ba-L or two macrophage-tropic HIV-1 primary isolates. Whatever the multiplicity of infection used, and in spite of high replication levels and an increase in HIV-infected cell frequency, neither significant IL-10 secretion nor IL-10 mRNA overexpression was induced in HIV-1-infected MDMs. Moreover, identical results were obtained with HIV-1-infected 1-day monocytes. These results show that MDM infection by HIV is not sufficient by itself for inducing IL-10 synthesis.