Lipid and acute-phase protein alterations have been described in various infection diseases, and they have been recorded during the early stages of HIV infection. Lipid and acute-phase protein profiles also have been correlated with cellular immunological abnormalities. To document these correlations during HIV infection, we studied 75 HIV-infected patients and 26 HIV-negative controls. Patients were classified according to the criteria proposed by the Walter Reed Army Institute: as WR-1 (CD4 lymphocytes, 1154 ± 268/mm³), WR-2 (CD4, 793 ± 348/mm³) and WR3/4 (CD4, 287±75 mm³). Triglycerides, total cholesterol and HDL-cholesterol concentrations were measured by enzymatic methods. Immunoglobulins (IgA and IgG) and acute-phase proteins (haptoglobin, a1-acid glycoprotein, C-reactive protein and transferrin) were determined by immunonephelometry. Haptoglobin levels were significantly increased in HIV-positive patients and correlated with the progression of HIV-infection (control<WR1<WR2<WR3/4). WR-2 and WR-3/4 patients had lower total cholesterol, HDL-cholesterol, and albumin concentrations, however, a1-acid glycoprotein and IgA levels were higher, when compared to HIV-negative controls. Elevated triglyceride levels (1.51±0.75 mmol/L) were found only in WR3/4 patients, when compared to the control individuals (1.05±0.04 mmol/L). No differences were found in transferrin and C-reactive protein concentrations among the studied groups. CD4+ lymphocyte counts were inversely correlated with triglycerides, IgA, a1-acid glycoprotein and haptoglobin, and they were positively correlated with albumin, total cholesterol and HDL-cholesterol. Multiple linear regression analysis showed that increased haptoglobin and IgA levels were the best predictive variables of a decreasing CD4+ lymphocyte count. In conclusion, our data showed that: 1) a decrease in total cholesterol, HDL-cholesterol and albumin levels occurred earlier than hypertriglyceridemia in the course of HIV infection; 2) increased levels of haptoglobin occurred earlier than that of a1-acid glycoprotein and IgA; 3) haptoglobin and IgA were the best predictive variables of a decreasing CD4+ lymphocyte count. Decreases in HDL-cholesterol and albumin levels with increases in haptoglobin, a1-acid glycoprotein, IgA, and triglycerides levels are indications of disease progression in HIV-infected patients.