Erythroid alterations were studied in 136 patients with rheumatoid arthritis (RA). Anemia was present in 75 cases. A definite diagnosis was determined in 65. The most frequent anemia was that of chronic disease (ACD) (43 cases); 14 patients with ACD presented with moderate to severe anemia. Prevalence of deficiencies were also high (15 cases had iron deficiency anemia, IDA). Serum erythropoietin levels were different in patients with RA compared with a healthy control group (p < 0.00001). Serum erythropoietin was increased in ACD (49 +/- 28.8 U/l) with respect to both RA (38.6 +/- 12.7 U/l, p = 0.0036) and controls (18.2 +/- 7.6 U/l, p < 0.00001). Although hemoglobin (Hb) was similar in ACD and IDA, serum erythropoietin in ACD was lower than in IDA (p = 0.01). There was a negative relationship between Hb and serum erythropoietin in ACD (r = -0.42, p = 0.005). In conclusion, almost 50% of patients with RA have anemia and ACD is the most frequent. As serum erythropoietin in ACD is blunted, patients with moderate to severe ACD are possible candidates for erythropoietin treatment.