  We present a technique for estimating the mass in the outskirts of galaxy
clusters where the usual assumption of dynamical equilibrium is not valid. The
method assumes that clusters form through hierarchical clustering and requires
only galaxy redshifts and positions on the sky. We apply the method to
dissipationless cosmological N-body simulations where galaxies form and evolve
according to semi-analytic modelling. The method recovers the actual cluster
mass profile within a factor of two to several megaparsecs from the cluster
centre. This error originates from projection effects, sparse sampling, and
contamination by foreground and background galaxies. In the absence of velocity
biases, this method can provide an estimate of the mass-to-light ratio on
scales ~1-10 Mpc/h where this quantity is still poorly known.
