Do Bilateral Investment Treaties succeed in attraction and encouragement of FDI inflows?; Do those treaties provide and guidelines when international investment law intersects with various social issues, particularly with human rights?; Considering that under the BIT system enormous power is given to foreign investment, do those treaties also grant equivalent rights to host states?; Is investors' rights equivalent to their obligations?; Do capital-importing states' rights correspond with their obligations as well? Those questions and issues are challenging the modern BITs considering that they are arising through the investment making as well as a whole lifespan of FDI, but the BITs, as the prominent features of international investment law, are silent in providing any succinct response thereto. This study analyses the efficiency of BITs under those issues. It argues that existing BITs pose certain challenges and proposes various legal, institutional and policymaking reforms. This work is recommended for lawyers, investors and students with an interest in international investment law, or anyone else who may be interested in international investment law, particularly in BITs