Plasma levels of LPS are increased in HIV-1–infected patients and are correlated with the proportion of circulating intermediate monocytes. Plasma samples from all donors were thawed and levels of LPS were measured using the limulus lysate assay. (A) Plasma levels of LPS were significantly increased in HIV-1–infected patients with controlled (< 400 copies/mL) and uncontrolled (> 400 copies/mL) viremia compared with levels in uninfected controls. (B) There was a modest and not significant correlation between plasma LPS levels and the proportion of CD14⁺⁺CD16⁺monocytes in the entire HIV-1–infected population. (C) There was a direct and significant correlation between plasma levels of LPS and the proportion of CD14⁺⁺CD16⁺ intermediate monocytes in patients with controlled viremia, but this correlation was not seen in patients with uncontrolled viremia (D).