Observations on beach firmness suggest that it is dependent on moisture content, average particle size, degree of sand sorting, and degree of packing of the beach sand. A method of multiple linear regression that may be extended to the nonlinear case is applied to the problem of "sorting out" empirically the relative effects of the controlling properties. The analysis involves several stages, in which the controlling factors are treated 1 at a time, 2 at a time, and so on, to allow for interrelations among the controlling factors themselves. A detailed example is presented for illustration of the method, and an appendix to the paper includes some theory as well as a summary of the IBM 650 program used in this study. A summary of several sets of data suggests that moisture content is the dominant control of firmness, with average grain size more important than degree of sand sorting. Some limitations in present data on sand packing hinder evaluation of this factor, but it appears to be less important than moisture content.