In research on cavitation, it is well known that the incipient cavitation number σ_inc is less than or equal to the desinent cavitation number σ_des. This condition is called “Cavitation Histeresis”. Authors observed how this condition could be affected by the time-dependent change of the system pressure. This test is named “the transient cavitation”. The delay time of cavitation after stepwise pressure drop, is concidered mainly affected by gas nuclei. From the experiments which is made under sinusoidal oscillation of the system pressure, it is revealed that in the region of lower velocity and higher frequency the incipient cavitation number was larger than the desinent cavitation number. However, this rather strange result is only tentative and quantitative, clearly indicating the need of further careful experimentation and analysis.