This paper presents the results of a theoretical investigation of the influence of developing cavitation zone on the rarefaction wave parameters in the region of regular reflection. The two-phase medium model is considered to represent a liquid with uniformly distributed cavitation bubbles of free gas. For the case of axial symmetry, on the basis of an assumption concerning the system of linearized equations for the two-phase medium motion, the dependence of pressure on free-gas concentration is obtained. This dependence, in conjunction with the non-linear equation for the cavitation bubble pulsation, allows the problem of the cavitation zone development and the rarefaction wave profile to be solved. The results of calculation for the negative pressure profile are given for the case of an explosion (at different depths) of a charge of 1 g by weight at initial volume concentrations of 10 −10–10 −11 of the free gas and the cavitation bubble radii of 5 × 10 −4–5 × 10 −5 cm. It is shown that for the case of instantaneous application of the negative pressure its action time is of an order of 0.1 μsec. If the rarefaction wave front inclination amounts to one or several microseconds, the maximum pressure in the rarefaction wave decreases by one or two orders as compared with the calculation for a one-phase liquid. The example of calculations of the visible cavitation zone development is given. The calculated data are compared with the experimental ones.