Considering macrophage migratory inhibitory factor (MIF) as a critical pro-inflammatory cytokine of the immune system, we evaluated plasma MIF levels in 89 HIV-infected adults. Plasma MIF levels were higher in HIV-infected than in HIV-negative individuals. Highest MIF levels were observed during acute HIV infection (AHI) whilst patients on antiretroviral therapy (ART) had lower MIF levels, regardless of ART efficacy. Our results suggest that MIF is an integral component of the cytokine storm characteristic of AHI.