We investigate basic properties of two-dimensional propagation and advection of compressible magnetohydrodynamic (MHD) perturbations in an axisymmetric equatorial solar wind with a spiral magnetic field. Analytical perturbation solutions at large radii are derived. In principle, numerical solutions which smoothly pass through both MHD fast and slow critical points can be constructed. In addition to wide applications of these solutions to small-scale small-amplitude compressible MHD fluctuations within the equatorial solar wind, we view large-scale MHD pressure waves and pressure-balanced structures (PBSs) as they evolve into large heliocentric distances, as a kind of nonlinear manifestations of MHD fast-mode and slow-mode disturbances in the solar wind, respectively. We discuss radial evolution of MHD fast waves for large-scale MHD pressure waves in their linear phase in the distant solar wind. We argue that it is natural to interpret PBSs in terms of MHD slow-mode disturbances at large heliocentric distances. We propose a scenario to identify PBSs with MHD slow-mode perturbations as well as their relation to MHD pressure waves based on the dissolution of a wave packet of compressible MHD disturbances in the interplanetary space. In principle, observational verification of this suggestion can be carried out by one or several coordinated spacecrafts. Furthermore, the analysis described here provides an important basis for two-dimensional numerical simulations of nonlinear interactions of interplanetary disturbances. Finally, we indicate that the minimum variance direction of magnetic field fluctuations in the present formation is along the radial direction. This result is consistent with the earlier WKB Alfv¿n wave normal analysis but is contrary to what is observed. ¿ American Geophysical Union 1994