Terahertz all-dielectric Electromagnetic Crystal (EMXT) waveguide to planar microstrip line transition structures are designed, simulated and fabricated. The design is similar to the ridge coupling structure used in metallic waveguide to microstrip transition. Simulation shows that the insertion loss of a back-to-back transition structure is 4 dB at 100 GHz. Experimental characterizations will also be reported. With this kind of transition structures, efficient integration of low loss all-dielectric THz waveguides to planar integrated circuits can be realized conveniently. © 2011 IEEE.