A well established property of late-type stars is that their rotation rate and their lithium abundance both decline with age. We understand why such stars are spun down while losing so little mass (Schatzman 1962), but we are still working on a theory which would explain all aspects of the observed lithium depletion. Although most agree that some kind of mixing must occur below the convective envelope of late-type stars, which transports 7Li to the depth where it is destroyed through nuclear burning, the physical process which is responsible for this transport is still in debate. However the most recent observations of the lithium abundance in close binary stars clearly show that there is a causal link between the destruction of lithium and the loss of angular momentum: consistently, tidally-locked binaries tend to display more lithium than single stars of the same effective temperature, as observed in the Hyades (Soderblom et al. 1990, Thorburn et al. 1993) and among old disk stars and halo stars (Spite et al. 1994).