[en] The electrical breakdown and discharge evolution in CO₂ laser-heated molecular gases has been studied. With the laser tuned to a vibrational mode of NH₃, C₂H₄, CH₂CHCN, or CH₃OH the breakdown potential decreases as much as 10-fold for laser pulse energies up to 35 J/cm². The subsequent 50--142-cm discharges are straight, stable, and reproducible. Analogous tests in D₂ and air yield only a small alteration of breakdown potential and do not cause a straight discharge. The expansion of the initial laser-heated gas has been modeled by the CHARTB hydrocode with the addition of the NH₃ equation of state in tabular and analytic form to that code. The breakdown characteristics and initial expansion stage confirm the earlier calculation of laser heating to 1900--2100 ⁰K. Experimental observations of the discharge evolution in NH₃ have measured (1) the radial expansion velocity by streak-camera photography of the H/sub β/ emission zone, (2) the plasma temperature by the Niv/Niii line-ratio method, and (3) the electron-density profile by holographic interferometry. The central zone of the channel is heated to 5.5 eV and expands with a radial velocity of 1.0--1.2 mm/μs for the case of a 27-kA discharge in 20 Torr of NH₃. Preliminary hydrocode simulations of the discharge show qualitative agreement with observations