Abstract.The buckling of long cylinders with homogeneous random axisymmetric geometric imperfections under uniform axial compression is studied by means of a modified truncated hierarchy technique. It is found that the buckling load of the cylinder depends only on the spectral density of the random imperfections. In particular, for small values of the standard deviation of the axisymmetric imperfection the buckling load depends only on the value of the spectral density at a specific wave number.1. Introduction. It is generally known that the buckling strengths of some structures are greatly reduced by the presence of small imperfections. However, the number of quantitative studies is limited. Furthermore, although it is recognized that these imperfections-geometric or otherwise-are generally random, very few investigators have used a statistical approach to the problem. Then it becomes routine to calculate the probability density of X* if a joint probability density is assigned to . In general, the analytic determination of the relation (1.1) is difficult if not impossible.Fraser calculates the buckling load of infinitely long imperfect beams on nonlinear foundations by assuming that the imperfections are homogeneous random functions and hence are characterized by their mean and autocorrelation. By means of the method of equivalent linearization he obtains the dependence of the buckling load on the spectral density of the imperfection.Like Fraser we assume that the cylinder imperfections are homogeneous random functions of the axial coordinate and hence are characterized by their mean and autocorrelation. The buckling of infinitely long imperfect cylindrical shells under axial compression is analyzed on the basis of a modified truncated hierarchy method.A model problem (the buckling of axially compressed infinite beams on linear stochastic foundations) is used to assess the validity of this technique. This problem is governed by a differential equation which is similar to the Karman-Donnell equations for cylinders when the latter equations have been linearized for investigating buckling phenomenon.