Objective To investigate whether methamphetamine (METH) can enhance human immunodeficiency virus 1 (HIV-1) infection in macrophages and the possible mechanism.Methods Peripheral blood samples were collected from eight healthy adult donors.Monocytes were isolated from blood samples and then cultured in vitro to induce differentiation to macrophages.These macrophages were treated with METH and/or dopamine receptor D1 (DRD1) antagonist,and then infected with HIV Bal strains.The levels of HIV RNA were measured in HIV Bal-infected macrophages by RT-PCR analysis.The real-time RTPCR was performed for the quantification of cellular DRD1.Results METH promoted HIV replication in macrophages in a dose and time dependent manner.This METH-mediated enhancement of HIV infection and replication in macrophages could be blocked by the DRD1 antagonist (SCH23390).Moreover,METH could induce the expression of DRD1.Conclusion METH might play a co-factor role in HIV infection in human macrophages by up-regulating the expression of DRD1.