Andy Mahdavi (San Francisco State University) Galaxy Clusters with CFHT: the Canadian Cluster Comparison Project Galaxy clusters are massive repositories of gas, galaxies, and dark matter. The best way to arrive at estimates of the dominant dark matter distribution is via gravitational lensing. We will provide an updated on a long-term project to measure the masses of 50 clusters studied as part of the Canadian Cluster Comparison Project. We examine the key sources of systematic error in cluster masses---these include shape measurement errors, which we constrain using simulations. Uncertainty in the determination of photometric redshifts is the largest source of systematic error for our mass estimates. We find that our lensing masses differ from hydrostatic mass estimates, which use gas thermodynamics to arrive at the total mass of the cluster. We discuss scaling relations and their implications for cosmology and cluster physics.