Results on the analytic behavior of the limiting spectral distribution of matrices of sample covariance type, studied in Marcenko and Pastur [2] and Yin [8], are derived. Through an equation defining its Stieltjes transform, it is shown that the limiting distribution has a continuous derivative away from zero, the derivative being analytic wherever it is positive, and resembles root\x-x(o)\ for most cases of x(o) in the boundary of its support. A complete analysis of a way to determine its support, originally outlined in Marenko and Pastur [2], is also presented. (C) 1995 Academic Press, Inc.