  The existence of magnetic fields associated with the intracluster medium in
clusters of galaxies is now well established through different methods of
analysis. The most detailed evidence for the presence of cluster magnetic
fields comes from radio observations. Magnetic fields can be investigated
through the synchrotron emission of cluster-wide diffuse sources and from
studies of the rotation measure of polarized radio galaxies. I will review
efforts to measure magnetic field strengths and power spectra and the main
issues that have led to our knowledge on magnetic fields in regular and
irregular clusters of galaxies.
