There is evidence that interleukin −10(IL‐10) interferes with the costimulatory properties of antigen‐presenting cells and, thereby, inhibits their ability to induce T cell activation. To determine whether this effect might involve modulation of the expression of accessory molecules, we analyzed by flow cytometry the influence of human IL‐10 on the basal expression of intercellular adhesion molecule 1 (ICAM‐1) as well as on the interferon γ(IFN‐γ)‐induced up‐regulation of ICAM‐1 and B7 at the surface of human monocytes. IL‐10 inhibited both the basal expression and the IFN‐γ‐induced ICAM‐1 up‐regulation. IL‐10 also reduced B7 up‐regulation on IFN‐γ‐stimulated monocytes. The inhibitory effect of IL‐10 both on ICAM‐1 and B7 expression was shown to be dose dependent. We conclude that the ability of IL‐10 to decrease both ICAM‐1 and B7 expression on monocytes might contribute to its immunosuppressive properties.