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Barring any fine tuning of the initial mass function of metal-free Population III stars, intermediate-mass black holes (IMBHs) may be the inevitable endproduct of the first episode of pregalactic star formation. We review a scenario for the assembly of supermassive black holes (SMBHs) at the center of galaxies that traces their hierarchical build-up far up in the dark halo ‘merger tree’, in (mini)halos collapsing at z ∼ 20 from the high-σ peaks of the primordial density field. As pregalactic IMBHs become incorporated through a series of mergers into larger and larger halos, they sink to the center owing to dynamical friction, accrete a fraction of the gas in the merger remnant to become supermassive, and form a binary system. Stellar dynamical processes drive the binary to harden and eventually coalesce. The binding energy liberated by shrinking SMBH pairs heats the surrounding stars, creating low-density cores out of preexisting cuspy stellar profiles. A simple model, where quasar activity is driven by halo major mergers and SMBHs accrete at the Eddington rate a mass that scales with the fifth power of the circular velocity of the host halo, reproduces surprisingly well the observed luminosity function of optically-selected quasars in the redshift range 1 < z < 6. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]