Interhemispheric conjugacy of auroral poleward expansion was studied using conjugate imaging riometers at ～67° inv. (invariant latitude) (Syowa Station, Antarctica, and Tjomes, Iceland) and at 75-77° inv. (Zhongshan Station, Antarctica; Longyearbyen, Svalbard and Danmarkshavn, Eastern Greenland). Ninety poleward expansion events at ～67° inv. observed in 1992-1993 were analyzed. The expansion at this latitude was characterized by a continuous poleward motion of cosmic noise absorption (CNA) bands with a velocity distribution that peaked at 1-1.5 km/s at a polar ionospheric altitude of ～90 km. The velocity distribution has another apparent peak at 3-5 km/s when measurements are made along the meridian. However, ～60% of the events forming this peak are overestimated because the motion of the CNA region's front was observed while the front was tilted away from the east-west direction. The difference in expansion velocities between conjugate stations remained within ±30% for half of the events. The time lag between the passage of a CNA band over conjugate stations was typically between 30-60 s. The product of this time lag and the poleward expanding velocity provides the location of the actual conjugate point. For 87% of the total number of events, the conjugate point for Syowa was located within ±200 km of Tjornes. The poleward expansion observed at 75°-77° inv. was characterized by a stepwise progression of CNA bands to higher latitudes. In other words, new CNA bands formed 50-180 km poleward of the preceding CNA band. The appearance of a new CNA band was often associated with an equatorward motion of the preceding CNA band. Equatorward moving CNA bands are thought to be located in a closed fieldline. The persistence of this band for several minutes was explained by pitch angle scattering of the trapped electrons as a result of a very stretched fieldline configuration in which the fieldline curvature was comparable to the Larmor radius of the trapped electrons. Although the conjugate pair used at these latitudes was displaced longitudinally by ～500 km, conjugacy was generally good. If a time lag of ±15 min is allowed, 52% of the CNA events observed at Longyearbyen had a counterpart at Zhongshan, and 40% had a counterpart at Danmarkshavn. This rather high level of conjugacy suggests that the characteristic longitudinal extent of the poleward expanding CNA bands is on the order of 500 km in the polar ionosphere.