The critical evaluations of the viscosity data of gaseous ethane and ethylene have been carried out based on the experimental data available in the literatures. All the experimental measurements under high pressure were critically evaluated in view of their reliability, and the data were correlated with temperature and pressure. The most probable values of the viscosity are presented in the form of numerical tables covering the range of temperature from 298.15 to 473.15K and that of pressure up to 700×10^5Pa for ethane, and from 297.15 to 373.15K and up to 800×10^5Pa for ethylene. The estimated uncertainties of the tabulated values are also given in the table. The relation between residual viscosity and density has been also examined over the whole range of temperature and pressure
