We have performed an ab initio mol. dynamics (MD) simulation of the structure of liq. hydrogen fluoride. Our results exhibit a strong contraction of the hydrogen bond in going from the gas to the liq. phase. The local structure of the liq. resembles that of the solid with the appearance of short lived hydrogen-bonded zig-zag chains. We have also studied the dynamic properties of the system. When compared with previous MD and Monte Carlo simulations based on empirical potentials our calcns. allow us to resolve old controversies. [on SciFinder (R)]