Directional leaky coaxial cables (DLCX) with periodic slots are proposed. The difference between this kind of leaky cable and the conventional LCX is that there are two rows of slots located oppositely on the outer shield of the coaxial cable. Different radiation patterns in the r-ϕ plane can be obtained by adjusting the relative distance between the two arrays. The radiation patterns and coupling loss are calculated by finite difference time domain method and dyadic Green's function. ¿ 2001 American Geophysical Union