Abstract: A one-dimensional high-latitude ionospheric model, in which the continuity, momentum and energy equations are solved self-consistently in the altitude range between 110 and 610km, is used to study the ionospheric responses to different upper boundary conditions. It is found that upper boundary conditions may influence significantly profiles of ionospheric quantities at higher altitudes. A larger upward O^＋ velocity at the upper boundary results in lower hmF2 and F region electron densities, and consequently higher electron temperatures. The difference in hmF2 between an upper boundary velocity of 0.0 m/s and 200 m/s reaches about 76 km. The altitude profiles of temperatures are quite different from each other corresponding to different upward ion velocities and heat fluxes from the magnetosphere. The Coulomb collisions between electrons and ions play an important role in shaping the electron temperature profiles at altitudes higher than the hmF2. The simulated electron temperature height profiles are similar to the measurements made in earlier studies. The altitude profile of electron temperature above 200 km is influenced by both downward heat fluxes and field-aligned O^＋ velocities, while the ion temperature and the electron density have their responses at altitudes higher than 250km. Proposals are given while specifying the upper boundary conditions in the simulation of the high-latitude ionosphere.