Studies in shock tubes have been extensive in recent years. These studies are directed in search of techniques to increase the effectiveness of gasdynamic lasers in which, as a rule, plane sonic and supersonic nozzles are used for the production of a jet issuing into free space or channel. The published experimental studies are primarily devoted to the measurement of quantum characteristics of GDL (amplification factor, power developed). At the same time, gasdynamic studies are few and concern mainly the determination of the wave structure of the jet, though relaxation of vibrational energy is determined by the distribution of gasdynamic parameters in the flow: velocity, temperature, pressure, and density. In computing the properties of gasdynamic lasers it is usually assumed that the jet is onedimensional and steady. However, experimental studies and computations [1-5] of jets brought out a number of significant features of the wave structure and the distribution of Jet parameters. It was shown that the flow past a nozzle section can have a fairly complex spatial structure which affects the characteristics of the laser beam. In particular, flow nonuniformity leads to phase nonuniformities in the laser beam which has an important bearing on the operation of laser at increased power conditions. Besides, in experiments with nozzles in shock tube it is necessary to keep in view that a transient flow process precedes quasisteady Jet efflux. In the present paper results are given for the experimental studies on three dimensional and plane jets in shock tubes under conditions similar to those in which studies on the laser characteristics [7, 8] of gas flows were conducted: transient time for the density field and the flow geometry, spatial characteristics of density distribution.