which dominates on scales that are much larger than a typical halo, is proportional to the auto-correlation of the halo population. In general the two terms are not expected to combine to produce a featureless power-law, but generally show a break or dip at the scale where the transition from the one-halo to the two-halo term occurs [@zehavi2004].

The extensive multi-wavelength spectrophotometric information that is now available for large numbers of galaxies allows us to estimate physical parameters of galaxies, such as stellar masses, instead of relying on observational properties such as magnitudes [@bell2001; @kauffmann03; @panter2004]. These estimates can even be obtained — with a proper measure of caution — for high redshift galaxies. Stellar mass estimates have been presented in the literature for galaxies up to redshifts as high as $z\sim 6$ [@yan2006; @eyles2007], and stellar mass function estimates have been presented up to $z\sim 5$ [@drory2005; @fontana2006; @elsner2008]. The goal of our paper is to develop a “Conditional Stellar Mass Function” (CMF) formalism, which is the stellar mass analog of the CLF. The CMF yields the average number of galaxies with stellar masses in the range $m\pm{\rm d}m$ as a function of the host halo mass $M$ and 