  The Red-Sequence Cluster Surveys (RCS-1 and RCS-2) are large optical imaging
surveys optimized to create well-characterized catalogs of clusters of galaxies
up to a redshift of ~1. We describe our first cosmological analysis, using the
self-calibration technique, of a cluster sample of ~1000 from the 90 sq. deg
RCS-1, using optical richness as a mass proxy. We obtain values for the
cosmological parameters $\Omega_m$ and $\sigma_8$ that are in excellent
agreement with the year-three WMAP results. Furthermore, the derived cluster
richness-mass relationship is entirely consistent with those measured directly
using dynamical mass measurements.
