  The coronal structure of main sequence stars continues to puzzle us. While
the solar corona is relatively well understood, it has become clear that even
stars of the same mass as the Sun can display very non-solar coronal behaviour,
particularly if they are rapid rotators or in a binary system. At masses
greater than and also less than that of the Sun, the non-solar internal
structure appears to affect both the geometry and dynamics of the stellar
corona and the nature of the X-ray and radio emission. In this talk I will
describe some recent advances in our understanding of the structure of the
coronae of some of the most active (and interesting) main sequence stars.
