There are two principal objectives of in-situ stress measurements in tunneling: ⊙ For the design of the tunnel support system: Evaluation of the primary (geologic) state of stress, usually carried out prior to the tunnel excavation and ⊙ for proof of the stress redistribution processes and the extent of the “Plastic Zone” around the tunnel: Evaluation of the secondary state of stress, usually carried out as a part of a tunnel monitoring programme. By definition, stress measurements are measurements at a point. Considering the highly inhomogeneous nature of rock a high degree of scatter of stress data is quite common. However, the most commonly used stress measuring methods (i.e. the overcoring methods) are not designed for carrying out a large number of measurements, as they are expensive and technically cumbersome. With the increased acceptance of alternative non-overcoring methods such as borehole slotting and hydraulic fracturing, the relevance of in-situ stress measurements has increased in recent years significantly. Examples of high-definition borehole slotting tests are presented from various regions of Central Europe which include the Ruhr destrict (deep coal mining), the Thuringian Forest (rock cavern) and the Alps (railway base tunnels). The examples are indicative of the new class of reliability with which both primary and secondary stress state around tunnels can be determined.