This study examines the interaction between plasmoids moving anti-sunward at high speeds and the tail lobes which bound them to the north and south. Attention is focused on the influence of changing lobe conditions with downtail distance. It is shown using ISEE 3 measurements that the gradual filling of the lobes with mantle plasma and the decrease in magnetic field intensity reduces the average lobe MHD fast mode speed from 1200 km s-1 at X=-80 RE to 400 km s-1 at X=-220 RE. This results in the ratio of the plasmoid speed to the fast mode speed increasing with downtail distance, from 0.3 at X=-80 RE to ~1 at X=-220 RE. It is argued that the ''standard'' traveling compression region (TCR) signature observed closer to the Earth will be distorted at large distances, where the fast mode transit time between the plasmoid and magnetopause becomes long compared to the time for the plasmoid to move past a given point in the tail. This change in the nature of the plasmoid-lobe interaction with downtail distance is offered as an explanation for why the reported rate of TCR occurrence peaks at X=-60 to -130 RE and decreases in the more distant tail. ¿ American Geophysical Union 1994