Phase locking has been achieved between two adjacent waveguide CO2lasers separated by a thin plate of ZnSe. Radiation leakage from one waveguide to the other through the ZnSe causes the phase locking, and stationary interference fringes demonstrate the relative phase stability. Both waveguide lasers are excited by dc discharges and operate on one of severalPorRtransitions in the 10.4‐&mgr;m band. Phase locking occurs whenever both waveguides are on the same transition. Annbymarray of such phase‐locked lasers has the potential of nearly an (n×m)2increase in the peak of the lasers’ far‐field irradiance distribution.