The 40Ar/36Ar ratio of the mantle bears important information about the extent of early degassing of the earth. Many researchers have agreed that 40Ar/36Ar ratio in the depleted mantle as sampled by Mid-Ocean Ridge Basalts (MORB) is as high as 28000. However, the 40Ar/36Ar ratio in the undepleted mantle has been strongly debated. We have reexamined the noble gas data of He and Ar in MORB and hot spot volcanics using 4He/40Ar vs 36Ar/40Ar and 4He/40Ar vs 3He/40Ar diagrams. In these diagrams, mixing lines between two components result in straight lines, which enable us to interpret data more easily than using diagrams with different denominators like a 40Ar/36Ar vs 3He/4He plot where all mixing lines appear as curves. We conclude that the 40Ar/36Ar ratio in the undepleted mantle is much higher than the atmospheric value and should be higher than the observed highest values in the hot spot volcanics. We also suggest that high 4He/40Ar ratios observed in MORB result from kinetic disequilibrium during partial melting. ¿ American Geophysical Union 1995