Some recent experimental and numerical studies were developed following previous works [Stutz et al. 1997b, 2000, Coutier 2004] and improving the physical analyses concerning unsteady behaviour of cavitating flows. Studies refer to a Venturi type section geometry characterized by a convergent angle of 18° and a divergent angle of about 8°. Recent experimental data are obtained by double optical probes measurements in cold water. A new method to treat experimental data, evaluate time-averaged values and standard deviations of the void fraction and the velocity field is proposed. Numerical calculations were performed with the 2D cavitating unsteady code "IZ", by applying two homogeneous approaches: the barotropic model proposed by [Delannoy 1990] and the void ratio transport equation proposed by [Kunz 1999]. No-reflecting boundary conditions, simulating the hydroacoustic behaviour of inlet and outlet pipes of the Venturi test section, were implemented and used to simulate cavitating flows. Unsteady local flow analyses were proposed from comparisons between experiments and simulations of unsteady cavitation in the considered Venturi geometry.