The present study was designed to investigate the possible relationships of hemoglobin concentrations with serum levels of soluble CD23 molecules (sCD23) and soluble tumor necrosis factor receptors I and II (sTNF-RI and sTNF-RII) in rheumatoid arthritis (RA) patients. Fifty-six patients, eight males and 48 females, and 20 age and sex matched healthy volunteers were enrolled in the study. Patients were classified in two groups on the basis of disease activity: group A included 43 patients with active, and group B 13 patients with non-active RA. Serum sCD23 and sTNF-Rs levels were measured using commercially available micro-ELISA kits. It was found that patients of group A had lower hemoglobin concentrations than patients of group B or normal controls, whereas hemoglobin levels in patients of group B did not differ statistically from the controls. Patients of group A had also significantly higher serum sCD23, sTNF-RI and sTNF-RII concentrations than patients of group B or control subjects. Serum levels of all three cytokines did not differ statistically between patients of group B and normal controls. In the entire group of subjects studied, hemoglobin concentrations correlated inversely with the levels of serum sCD23, sTNF-RI and sTNF-RII, and also with the values of the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) reflecting disease activity. We concluded that anemia and elevated concentrations of sCD23, sTNF-RI and sTNF-RII in RA patients are two biological expressions of the same underlying inflammatory process, although a causal relationship between themselves cannot be excluded and needs further investigation.