  The CAIRNS (Cluster And Infall Region Nearby Survey) project is a
spectroscopic survey of the infall regions surrounding eight nearby, rich,
X-ray luminous clusters of galaxies. We collect 15665 redshifts (3471 new or
remeasured) within \sim 5-10 Mpc of the centers of the clusters, making it the
largest study of the infall regions of clusters. We determine cluster
membership and the mass profiles of the clusters based on the phase space
distribution of the galaxies. All of the clusters display decreasing velocity
dispersion profiles. The mass profiles are fit well by functional forms based
on numerical simulations but exclude an isothermal sphere. Specifically, NFW
and Hernquist models provide good descriptions of cluster mass profiles to
their turnaround radii. Our sample shows that the predicted infall pattern is
ubiquitous in rich, X-ray luminous clusters over a large mass range. The
caustic mass estimates are in excellent agreement with independent X-ray
estimates at small radii and with virial estimates at intermediate radii. The
mean ratio of the caustic mass to the X-ray mass is 1.03\pm0.11 and the mean
ratio of the caustic mass to the virial mass (when corrected for the surface
pressure term) is 0.93\pm0.07. We further demonstrate that the caustic
technique provides reasonable mass estimates even in merging clusters.
