The Chuo Expressway Fuchu Pavement Section has been in service and in good condition for morethan 20 years without any repair work. The contractor was awarded a letter of appreciation by the President of Japan Highway Public Corporation (JHPC) in 1991 for this excellent pavement. The reason for the high durability of this pavement was investigated analytically and experimentally. It is concluded that the key is the asphalt mixture of the surface course. The procedure for calculating the voids in mineral aggregate was proposed and its validity was demonstrated by the experimental results.