This book represents the proceedings of a NATO Advanced Study Institute which was held at Bonas from August 25 till Sep tember 5, 1980 and was devoted to the study of "Solar Phenomena in Stars and Stellar Systems." It is intended for a broad audi ence. Students and post-doctoral scientists for example can dis cover new aspects of astrophysics. The general spirit of the ASI was aimed at presenting a unified aspect of astrophysical phenomena which can be studied intensively on the Sun although they are of a much more general nature. On the other hand, spe cialists in solar or stellar physics...