Cavitation characteristics of liquid hydrogen and liquid nitrogen flowing in a transparent plastic venturi were determined and conventional cavitation-inception-parameter curves are given.Representative developed-cavitation data, consisting of pressure and temperature measurements within fully-developed cavities, are also given; measured temperatures and pressures within the cavities were generally not *in thermodynamic equilibrium.Existing theory was used to obtain equations which correlate the experimental data for developed cavities in liquid hydrogen or liquid nitrogen.The theory is extended to include the effect of cavity thickness and the experimental data are used to evaluate the results.Some recommendations for future work are given.(Author).