Corruption is a complex and multifaceted phenomenon. The aim of this article is to open the “black box” of corrupt transactions using the framework of the New Institutional Economics. First, it examines “corrupt contracts”, the institutions that promote them, the mechanisms involved, the transaction costs and the problems faced by the actors. Then the stages of a typical corrupt agreement are described: initiation, execution and post-contractual phase. To combat corruption the understanding of how corrupt actors think and how corrupt agreements work is necessary. Finally, the potential and limitations of traditional and the more recent anti-corruption measures are analyzed.