The solar-terrestrial interaction is dominated by reconnection between the IMF and the Earth's magnetic field and the consequences which follow from this. Momentum and energy transfer from the solar wind into the magnetosphere are controlled by the direction of the IMF. Other factors such as the magnitude and length of time in certain directions are also important. In this paper we discuss the role played by reconnection in the process and its importance for Space Weather. (C) 2000 COSPAR. Published by Elsevier Science Ltd.