A particular configuration of the LHD stellarator with an unusually flat pressure profile has been chosen to be a test case for comparison of the MHD stability property predictions of different three-dimensional and averaged codes for the purpose of code comparison and validation. In particular, two relatively localized instabilities, the fastest growing modes with toroidal mode numbers n = 2 and n = 3, were studied using several different codes, with the good agreement that has been found providing justification for the use of any of them for equilibria of the type considered. (C) 1996 Academic Press, Inc.