Long-term natural gas supply agreements have for decades been the backbone of the European gas supply system. The traditional view was that these contracts provide for security of demand for the producer and security of steady supply for the purchaser. However, due to the progressive liberalisation of gas supply markets this traditional setting has now started to change. Many European customers have access to spot markets and the development of international pipelines might further strengthen this alternative source. Therefore, the specific features of long-term gas supply agreements are currently at the forefront of legal and political discussions in Europe. Issues like oil price indexation, price reviews, flexibility and take-or-pay clauses are being debated, all of which are areas where competition law is playing an increasingly important role.