The work hardening characteristics of LiF single crystals in compression and tension has been investigated as a function of temperature. It was shown that in temperature range from 200 "C to 600 "C four stages of hardening were observed and the main part of plastic flow proceeds in stage IV. The parabolic hardening was not observed. The flow stresses and hardening rates in all stages in compression are higher than those in tension. As a temperature increase this difference decreases. The hardening rates, stresses which correspond to the beginning of the linear hardening stages and the duration of those stages decrease as a teiiiperature increase. At temperatures above 600 "C the yield drop occured. Taking into account a good agreement between the temperature dependences of the critical resolved shear stress and t 1 1 1 the assumption was made that 7111 corresponds t o resolved shear stress in a secondary glide system. H3yYeHbI MeXaHHYeCKHe CBOfiCTBa MOHOKpHCTaJlJlOB LiF npH CXaTHIl