Background/Aims: We studied the relationship between hemoglobin (Hb), which is a major buffer of blood, and arterial blood total carbon dioxide (tCO<sub>2</sub>) levels in maintenance hemodialysis (HD) patients. We also evaluated the difference between the tCO<sub>2</sub> measured with a standard Hb value of 15 g/dl, and that assayed with an actual Hb level entered into an analyzer. Methods/Results: In 105 patients the predialysis tCO<sub>2</sub> level of 21.4 ± 2.84 mEq/l inversely correlated with the Hb level of 9.5 ± 1.78 g/dl (r = –0.358, p = 0.0002). This indicated that the rise in Hb from 6 to 14 g/dl could result in a decrease of about 5 mEq/l in the tCO<sub>2</sub> level. In 20 patients the tCO<sub>2</sub> level measured at the Hb of 15 g/dl was 21.0 ± 2.47 mEq/l, and higher (p = 0.009) than that of 20.8 ± 2.45 mEq/l estimated at the actual Hb. The difference between these two measurements was inversely associated with the Hb level (r = –0.579, p = 0.007). The measurement of tCO<sub>2 </sub>at the unadjusted Hb slightly underestimated the degree of acidosis when the actual Hb level was < 11.5 g/dl. Conclusion: The degree of anemia and, to some extent, laboratory technique should always be considered when interpreting changes in arterial blood acid-base balance in maintenance HD patients.