The anisotropy of the density fluctuations in the solar wind is studied with the assumption that density fluctuations are connected to magnetosonic turbulence. It is shown that the anisotropy of density fluctuations does not coincide with that of the turbulence energy in the case of the fast magnetosonic waves while they are equal for the slow magnetosonic waves. The radial evolution of the two-dimensional (2-D) anisotropy ratio in the interplanetary scintillation (IPS) pattern plane due to the change of the ambient magnetic field direction is investigated. In the case of the Parker's spiral magnetic field the radial dependence of the 2-D anisotropy ratio is shown to be considerably stronger for the fast magnetosonic waves than for the slow magnetosonic waves. The comparison between theoretical estimations and the results of the Kashima high-frequency IPS measurements shows that the geometric effects are not sufficient to account for the observed radial dependence of the axial ratio, and that the angular distribution of turbulent energy evolves in the region of heliocentric distances between 0.1 and 0.4 AU toward the state enriched by the magnetosonic waves propagating at smaller angles relative to the ambient magnetic field. The nonlinear wave-wave interactions seem to be responsible for this evolution of the density turbulence spatial power spectrum. ¿ 2000 American Geophysical Union