Abstract: Objective To explore the impact of human immunodeficiency virus(HIV)infection status on the severity of plasmodium vivax malaria.Methods Twelve patients with HIV infection(all signed informed consent)whose CD4 count baseline levels were 1 217~15×10⁶/L were intravenously injected with plasmodia vivax to induce ther apeutic malaria.Malaria was teminated with chloroquine after 10 fever episodes.Correlations of CD4 cell count baseline levels to the areas under temperature curves (Tsq,represents clinical severity of malaria)and to parasite densities were statistically analyzed.Results The CD4 count baseline levels of the HIV-infected subjects positively correlated to their clinical severities of malaria(r=0.819,P<0.05)and to their parasite densities of peripheral blood(r=0.807,P<0.02).These phenomena indicated that the HIV-positive patients had milder malarial symptoms and parasitemia with progressively lower CD4 cell baseline levels.Conclusion The results suggested that there was an antagonistic interaction between HIV and malar ial parasite in human.