Adherent cells and serum components from Kenyan patients with visceral leishmaniasis were examined with the view to evaluating their contribution to cell-mediated immune suppression. Mitogens (phytohemagglutinin and concanavalin A) and antigens (purified protein derivative, streptokinase-streptodornase, and leishmania) were used as stimulants. Compared to the controls, the contribution of serum components to suppression in presence of any of the mitogens and antigens was not significant. The same applied to adherent cells, except in the presence of leishmania antigen where adherent cells contributed significantly (P < 0.001). Removal of adherent cells from peripheral blood mononuclear cells of patients and controls considerably increased in vitro lymphocyte responses to both mitogens and antigens (by about twice), suggesting that in this study, the inhibition of in vitro lymphocyte responses to antigens and mitogens by adherent cells was a general phenomenon independent of the presence of the disease.