Until now, the historical cost principle has dominated accountancy. At this time, another principle seems to operate: the fair value principle. The discussion will gravitate around the questions: What is fair value? How has concept of fair value evolved? How much is the fair value used as the basis for measurement in IFRS? Are we moving towards a full fair value? In conditions of economic crisis, the measurement at fair value offers pertinent information? To answer at these questions, we have realized by one hand, a description of the manner which the notion of fair value evolved and in the other hand, a deep IFRS analysis which use fair value in assets and liabilities evaluation. As a result of this study, it seems that the most of the assets and liabilities need to be measured at fair value or they may be measured at fair value, if the entity chooses this accounting treatment.