We analyse statistically the infall of mass onto clusters in $\Lambda$-CDM numerical simulations. Also, we consider numerical simulations which include galaxy formation through semi-analytical models to compare the expected infall of mass and galaxies. We find the most probable values at $V \sim 300-400$ km/s and a significant tail of large infall velocities ($V > 1000$ km/s). The flow onto cluster is more pronounced for high local density regions. Mass and galaxies behave similarly although with a slightly lower amplitude.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html