The viscosity of H-2-CO2 mixtures at 500 K, 800 K, and 1100 K, 3 x 10(5) Pa pressure, and (15, 30, 50, 70, and 85) mol % CO2 has been measured experimentally. The experimental methods make use of the fact that in the laminar flow regime the flow rate is inversely proportional to the fluid viscosity for a given pressure gradient.