Abstract. In this paper we define a class of truth-value assignments, called bounded assignments, using a certain substitutional property. We show that every satisfiable Boolean formula has at least one bounded assignment. This allows us to show that satisfying truthvalue assignments of formulas in USAT can be syntactically defined in the language of classical propositional logic. We also discuss a possible application of bounded truth-value assignments in local search and other methods for solving Boolean satisfiability problems.