This article builds on Ajzen's theory of planned behavior and on Stern et al.'s value-belief-norm theory to propose and test a model that predicts proenvironmental behavior. In addition to relationships between beliefs, attitudes, and behaviors, we incorporate Inglehart's postmaterialist and Schwartz's harmony value dimensions as contextual antecedents at the national level. Structural equation modeling analyses of a 27-country sample provide almost full support for the mediation model. Postmaterialistic values, but not harmony, affect environmental concern; in turn, environmental concern, perceived threat, and perceived behavioral control affect willingness to sacrifice, which then affects a variety of proenvironmental behaviors. The findings emphasize the contribution of cultural conditions to the shaping of individuals' actions vis-a-vis environmental issues, alongside individual-level social-psychological variables. (Contains 2 figures, 2 tables, and 9 notes.)