Employing the principle of a phase‐locked loop (PLL) we have synchronized the frequency and phase of two CO2lasers. The laser acting as voltage controlled oscillator is tuned both by electro‐optic and piezoelectric means. A cooled photodiode serves as the phase detector. The main loop parameters, natural frequency &ohgr;nand damping factor &zgr;, have been measured. The small phase jitter in the error signal obtained will allow application of such an optical PLL in homodyne receivers at 10 &mgr;m.