This article describes the activities of espionage and counter-espionage conducted by the ministry of security of the German Democratic Republic (Stasi) during the time of the détente. The policy of opening towards the West caused the Stasi to be burdened with a wide range of new duties. Thus, its apparatus grew substantially. By analyzing the broad German literature on this topic this article aims at showing the development of the Stasi and, generally, its articulated reaction in facing those important political changes.