A potential energy surface has been derived using ab initio and spectroscopic data for the lowest (2)A' State of LiH2, Quasi-classical trajectories have been carried for the astrophysically important reaction LiH(X,(1)Sigma (+)) + H(S-2) --> Li(S-2) + H-2(X, 1 Sigma (+)(g)). Between 150 and 4000 K the rate is 2-6 x 10(-10) - 6 x 10(-10) cm(3) molecule(-1) s(-1) and a satisfactory analytical fit to this is 8.4 x 10(-13)T exp(-0.0004T) while below 150 K the rate goes as 4.36 x 10(-11) T-0.28 cm(3) molecule s(-1) which is close to that expected from the long-range behaviour of the electronic energy. The reaction is exothermic by about 2 eV which is disposed of largely in high vibrational states of H-2(X,(1)Sigma (+)(g)).