The interplanetary medium is characterized by a heliospheric current sheet (HCS), a heliospheric plasma sheet (HPS) in which the HCS is embedded, a slow wind astride the HCS and HPS, and a fast wind at high latitudes. In terms of perpendicular shock approximation, a simplified one-dimensional analysis is presented on the interaction between interplanetary shocks and the HCS, HPS, and the slow wind. It is shown that the HCS alone is transparent for the shock transmission and thus does not affect the shock propagation at all, whereas the HPS is too thin and the density ratio between the HPS and its surroundings is too low to produce appreciable effect on the shock transmission. On the other hand, the slow wind astride the HCS and HPS does exert a significant influence on the shock which is weakened in strength after its transmission, and the shock speed is significantly reduced both during and after the transmission. Therefore we conclude that it is not the HCS and HPS but the slow wind associated with them that affects the interplanetary shock propagation. Although the interaction of the HCS and HPS on interplanetary shocks is negligible, both HCS and HPS are distorted in shape and internal structure under the action of the shock. These conclusions are demonstrated by 2.5-D MHD numerical simulation examples. ¿ 2001 American Geophysical Union