A highly ionized plasma in helium at a pressure of 10 atm was produced by a giant laser pulse. The properties of the plasma were studied by a dc helium‐neon gas laser. Measurements of the variation of the shape and size of the plasma, its electron density and temperature, and its absorption coefficient at 6328 A˚ were made during the afterglow between 100 and 600 nsec. The shock wave emitted by the plasma was also studied.