In this article notions from literature on covert and illegal networks are applied to business cartels. Comparable to most criminal networks, cartel participants need to communicate in order to coordinate their activities, whilst under the risk of getting caught. Previous studies however show cartels can remain hidden from outsiders for long periods of time. Based on an analysis of fourteen Dutch cartel cases, this article addresses the question how cartels can remain hidden from outsiders for long periods of time. The analysis shows cartel participants communicate predominantly centralized and frequent. Moreover, the results show that not concealment but social embeddedness provides a strong explanation for the longevity of secrecy regarding cartels.