  Study of radio supernovae (RSNe) over the past 20 years includes two dozen
detected objects and more than 100 upper limits. From this work we are able to
identify classes of radio properties, demonstrate conformance to and deviations
from existing models, estimate the density and structure of the circumstellar
material and, by inference, the evolution of the presupernova stellar wind, and
reveal the last stages of stellar evolution before explosion. It is also
possible to detect ionized hydrogen along the line of sight, to demonstrate
binary properties of the stellar system, and to show clumpiness of the
circumstellar material. More speculatively, it may be possible to provide
distance estimates to radio supernovae.
  The interesting and unusual radio supernova SN 1998bw, which is thought to be
related to the gamma-ray burst GRB 980425, is discussed in particular detail.
Its radio properties are compared and contrasted with those of other known
RSNe.
