These are the Proceedings of Colloquium No. 153 of the International Astro- mical Union, held at Makuhari near Tokyo on May 22 - 26, 1995, and hosted by the National Astromical Observatory. This meeting was intended to be an interdisciplinary meeting between re- searchers of solar and stellar activity, in order for them to exchange the newest information in each field. While each of these areas has seen remarkable advances in recent years, and while the researchers in each field have felt that information from the other's domain would be extremely useful in their own work, there have t been very many opportunities for intensive exchanges of information between these closely related fields. We therefore expected much from this meeting in pro- viding stellar researchers with new results of research on the counterparts of their targets of research, spatially and temporarily resolved, as observed on the Sun. Likewise we hoped to provide solar researchers with new results on gigantic ver- sions of their targets of research under the very different physical circumstances on other active stars. It was our greatest pleasure that we had wide attendance of experts and active researchers of both research fields from all over the world. This led to extremely interesting talks and very lively discussions, thereby stimulating the exchange of ideas across the fields.