S>The method of Hess for determining lattice parameters annd their standard errors from x-ray powder diffraction films was investigated. The equations are applicable to various cameras and crystal systems. The results of a series or computations in which the initial approximations were deliberately varied over wide that for the computation of precise lattice parameters, the initial estimates need not be good. A parameter input value of zero should be avoided, but otherwise almost any value will do. (J.R.D.)