We have evaluated the accuracy of a simple and inexpensive photometric device (DHT) for the estimation of the blood concentration of hemoglobin by comparison with an automated, high-resolution, flow cytometry-based hematology analyzer (CellDyn 3000) and a centrifugal quantitative buffy coat hematology system (QBC I). We have analyzed the hemoglobin values of 163 individual blood samples. Bland-Altman analysis showed that the methods agreed only poorly: mean differences were 1.0 g/dL with limits of agreement (LOA) of -1.2 g/dL to 3.2 g/dL for the comparison of DHT and CellDyn measurements, 0.5 g/dL with LOA of -2.0 g/dL to 3.0 g/dL for the comparison of DHT with QBC measurements, and 0.5 g/dL with LOA of -1.1 g/dL to 2.1 g/dL for the comparison of QBC with CellDyn measurements. We conclude that the poor agreement of the DHT with the CellDyn does not permit the use of the DHT for critical hemoglobin measurements, particularly in transfusion services.