The development of the United Nation’s Convention on Contracts for the International Sale of Goods (CISG) started at the beginning of the 20th century in order to provide a uniform legal regime for international sales contracts. The development started because of a belief that a uniform international sales convention would contribute certainty in commercial trade and decrease transaction costs for the contracting parties. The Convention was signed in Vienna 1980 and came into force in 1988 after securing the necessary number of ratifications. The CISG is automatically applied to international sale contracts in certain given situations but the contracting parties are free to exclude the Convention as applicable law in favour of another regulation. As of today, more than 25 years after the CISG came into force, the Convention is commonly being excluded as the governing law of international sales contracts. By studying surveys and academic writings, certain factors can be derived as reasons prior to an exclusion of the CISG. The factors can be referred to as unfamiliarity, time and costs, negotiation strength and standard form contracts or standard terms. Regarding unfamiliarity, the importance given to the Convention in law faculties within the signatory states, together with time and costs attributed to a familiarization process, seems to play an important role. Moreover, the Convention is associated with problems regarding a non-uniform interpretation of the Convention’s provisions within the national courts and arbitral tribunals, as well as regarding its incompleteness, meaning that there are gaps that need to be filled by national law. These problems affect the Convention’s ability to provide potential users with legal certainty and predictability, which in turn may affect the familiarity with the Convention and hence have an impact on an exclusion of the CISG.