The structures of expanded liquid alkali metals, Na. K, Rb and Cs, along the Liquid-vapour coexistence curve are investigated theoretically by employing the integral equation method in the modified hypernerted-chain (hIHNC) approximation and the molecular dynamics (m) simulation. Excellent agreement is obtained between the MHNC and the MD results, which also agree well with the experimental results. It is shown from lhese systematic investigations that the characteristic features of the density dependence of the structure alongthe liquid-vapour coexistence curve observed for expanded liquid Rb (Franz er01 1980) andCs (Winterelal1987) arecommon featuresforexpanded liquidalkali metals.