Sudden changes in the solar wind dynamic pressure have been linked, both theoretically and observationally, to the formation of a number of transient ionospheric phenomena. Still, the precise role that these pressure changes play in the formation of these phenomena remains uncertain. By using a combination of ground-based magnetic measurements from arrays of magnetometers located in Greenland and IMP 8 satellite measurements of the solar wind velocity and density, we have been able to better study the effect that pressure changes have on the high-latitude ionosphere. Our study is based on approximately 2500 hours of solar wind plasma data collected during 1991 and 1992 by the IMP 8 satellite and focuses on step changes of |Δp|>2 nPa, occurring on a timescale of Δt<15 min. We have found that the ground response does not consistently conform to existing theoretical models of field-aligned currents generated by changes in dynamic pressure. We also do not find any explicit dependence on interplanetary magnetic field orientation. These results lead us to believe that the nature of the ground response is due to a more complicated combination of external controls. ¿ American Geophysical Union 1996