Methodology for thermochemical evaluating reactivity of solid phases in nonstandard states is proposed. both amorphous and crystalline reagents being considered. The principal attention is paid to baroinduced states of solid reagents. Analytical expressions both for calculating baroinduced increments of thermochemical quantities and for linearized evaluating these quantities at polymorphic transformations are derived. The criterion for differentiation of activating and passivating pressure effects at solid-state transformations is advanced. The influence of crystal structure symmetry on its baroinduced reactivity is analyzed. Parameters for practical calculations are tabulated. (C) 2012 Elsevier B.V. All rights reserved.