The main objective of this drilling fluid analysis was the detection of inflows of formation fluids. Therefore different gases dissolved in the drilling mud were measured continuously and automatically at drill site with three different methodes (Fig.: KTB-Report 92-2 page C13). The operation principles of the mass spectrometer and the gaschromatograph have been explained by STROH et al. (1988) and FIGGEMEIER et al. (1991). The principle of radon determination is published by ERZINGER et al. (1992).