  Some issues relevant for the formation of supermassive black holes are
discused and estimates of the event rates for the emission of gravitational
waves by coalescing supermassive black hole binaries are given. The models take
into account recent improvements in our knowledge of galaxy and star formation
in the high-redshift universe. Estimated event rates range from a few to a
hundred per year. Typical events will occur at redshift three or larger in
galaxies lying at the (very) faint end of the luminosity function at these
redshifts.
