We report on the generation of an efficient phase-conjugate wave by anisotropic four-wave mixing in planar iron-doped y-cut LiNbO₃ waveguides. The pump waves are orthogonally polarized with respect to the signal and phase-conjugate waves. Reflectivities of the phase-conjugate signal of as much as 65% are reached in the waveguide. Experimental results are compared with numerical solutions of the corresponding system of coupled-wave equations. © 1992 Optical Society of America.