Abstract The dehydrogenation of ethyl alcohol on LiF single crystal surfaces has been investigated to determine the role of surface dislocations and another defects on the catalysis. The catalytic activity of the single crystal of LiF was greatly influenced by the surface treatments such as the manners of cleaving of the crystal and vacuum heating and so on. After radiation quenching subsequent to vacuum anealing at 350°C for 2 hr, the catalytic activity was greatest in the present work, being over seven times greater than that of nontreated crystal. The catalytic activity after the quenching treatment was found to increase in proportion to logarithm of the dislocation density. In observations with the electron microscope, the small spots concentrated in the center of dislocation was found on the highly activated crystal surface. From the results of kinetic and microscopic observations discussion was made on the catalytic sites of the LiF single crystal.