Results obtained with the University of California, Irvine gas‐puff Z‐pinch experiment are described for deuterium and deuterium‐argon mixtures. This experiment utilizes a hollow cylindrical gas puff injected between electrodes driven by a 4.8‐kJ capacitor bank. Various gas compositions have been tested, including pure deuterium, 90% D2‐10% Ar, and up to 10% D2‐90% Ar. We have observed the stages of collapse and its rate, electron density at the pinch, neutron yield, and the time dependence of x‐ray and neutron emission. When a 90% D2‐10% Ar mixture is injected, the plasma annulus is observed to separate into two columns which implode concentrically.