  The GMRT Radio Halo Survey, carried out at 610 MHz to investigate the
statistical properties of cluster radio halos in a complete cluster sample
selected in the redshift interval z=0.2-0.4, has significantly improved our
understanding of the origin of cluster radio halos and relics. Here we briefly
summarize the most relevant results of our investigation. A low frequency
follow-up is in progress with the GMRT at 325 MHz and 240 MHz on the diffuse
sources and candidated found at 610 MHz. We briefly report some preliminary
results on these low frequency observations. Cluster radio halos with different
radio spectral properties have been unexpectedly found.
