Ideal MHD stability limits of anticipated plasma configurations for NSTX [Ono M. et al 2000 Nucl. Fusion40 557] and the dependence on the parameters defining the MHD equilibrium are evaluated. The study provides a quantitative computational evaluation of the stability limitvariations induced by changes to the equilibrium of NSTX high β plasmas. The analysis is based on a reference free-boundary equilibriumwith β = 41.5%, monotonic safety factor q profile (qa = 12.1, q0 = 2.8) and broad pressure profile p (peaking factor Fp≡p(0)/⟨p⟩ = 1.7). On this reference target local variation of the plasma boundary,and the safety factor q and pressure profiles p are imposed. Localized inflection of the outboard plasma boundary, produced by near field effects from poloidal shaping field coils, weaken the stability due to the destabilization of high n ballooning modes. Variation of the qprofile at different radial locations can also degrade stability. Both experimental profiles from existing tokamaks and spherical torus machines and profiles generated from transportmodelling of anticipated neutral beam heated plasmas are used. Degraded stability is found at increasing pressure peaking factor due to the destabilization of n = 1 kink/ballooning modes. Direct access to the second region of stability is found in certain configurations and, for the entire set ofvariations considered, the lower calculated β limit values are still inthe range of 20.0% without considering the stabilizing effect of thepassive conducting structures.