The plasmadynamic recombination laser concept is verified experimentally in a high‐power quasisteady MPD arcjet operating at 4 kA and 12 g/sec of argon. Measurements of the spatial variation of electron temperature electron density, and population densities in the arc exhaust flow confirm that inverted populations of the 4pto 4sArII transitions are established by collisional‐radiative recombination of the ArIII ion. Using an optical cavity aligned transversely to the flow, recombination lasing of four such transitions, 5145, 4880, 4764, and 4727 A˚, is observed spectrophotographically and photoelectrically over the entire 1‐msec discharge.