The expression and co-expression profiles of functionally important monocyte surface markers were compared between control and HIV+ individuals using combined physical gating and dim CD4 expression to delineate the monocytes. The Fc gamma RII (CD32), the MHC class II antigen HLA-DR and the adhesion molecules CD11a (LFA-1 alpha), CD18 and CD54 (ICAM-1) showed an unimodal distribution. Of these markers, CD11a and HLA-DR were up-regulated in the HIV+ subjects compared with controls. The expression levels of the adhesion molecules correlated with each other in both patients and controls. The CD11b (CR3-alpha), CD14, Fc gamma RI, and Fc gamma RIII markers were bimodally distributed. Compared with controls, monocytes from seropositives contained fewer CD14bright+ cells, an equal proportion of Fc gamma RIbright+ cells, but twice as many Fc gamma RIII+ cells. The expression level of Fc gamma RI and CD11b within their brightly positive subset increased as CD4 T cells decreased. Both in patients and controls, co-expression of bright CD11b, CD14 and Fc gamma RI was shown, whereas the Fc gamma RIII+ cells were negative or dim positive for the former triad. We conclude that the expression of two Fc gamma R (I and III), of the adhesion molecules CD11a and CD11b and of HLA-DR showed particular alterations on monocytes from HIV+ subjects. The relationship of these phenotypic observations with altered cytokine profiles and altered monocyte function is discussed.