A new equation for estimating liquid viscosity of pure compounds in a corresponding-state group-contribution method (CSGC) is presented. Group-contribution parameters of 84 groups were obtained by correlating experimental liquid viscosity data at different temperatures (a total of 2777 data points) of 366 compounds including various alkanes, alkenes, cyclohydrocarbons, aromatic and oxygenated hydrocarbons as well as compounds containing sulfur. nitrogen and halogen. The new method demonstrates significant improvement in accuracy.