Altogether 98 focal mechanisms of micro to moderate earthquakes (ML = 0.5−5.9) have been used to analyze the state of stress in the Rhine Graben and adjacent areas. Due to dense networks in the investigated area fault plane solutions determined by the first motion method can be fixed with an accuracy better than 10°. The majority of the focal mechanisms is characterized by strike-slip and normal faulting movements; only a few events are of reverse faulting type.To calculate the orientations of the principal stress axes and the shape of the stress tensor we applied the inversion method of Gephart and Forsyth (1984) to three subsets of the data, each of which has been chosen taking into account the local tectonic units (northern Alpine foreland, southern Rhine Graben, northern Rhine Graben including Rhenish Massif and lower Rhine Embayment). For all of the data subsets, the inversions revealed a stable axis of minimum principal stress σ3, oriented horizontally to subhorizontally and striking in a WSW-ENE to SW-NE direction. The azimuth of σ1, the maximum principal stress, is about 150°. However, the confidence regions show that horizontal and vertical orientations of σ1, as well as orientations in between, are of the same probability. Therefore, an unequivocal distinction between strike-slip and extensional regimes is not possible. When comparing the results from the data subsets, a slight counterclockwise rotation from south to north of about 30° of the σ1−σ2 plane plane as well as of the direction of σ3, can be observed. The relative stress magnitude R (R = (σ2 − σ1)/(σ3 − σ1)) has a value of about 0.5 for all subsets, indicating that for the deviatoric part of the stress tensor, σ1 and σ3 are of the same magnitude but of opposite sign. The directions of the horizontal stresses, SHmax and Shmin, inferred from the analysis of focal mechanisms are in good agreement with the general features for western Europe in the European Stress Map.More detailed investigations have been performed for the southern Rhine Graben area. A division into an upper crustal (<15 km) and a lower crustal (>15 km) dataset makes possible the resolution of an individual stress regime for each subset: a strike-slip regime for the upper and an extensional regime for the lower crust, with the same azimuths of the principal stress axes for both depth ranges. Such a change of the stress tensor with depth fits into the tectonic model of detachment zones in the lower crust in the northern front of the Alps, a detachment caused by south-plunging subduction of the European plate beneath the Alps and the Adriatic plate.On the basis of the resolved orientations of the principal stress axes and the shape of the stress tensor, we furthermore estimated absolute stress magnitudes and the ranges of frictional parameters acting on the individual faults. Assuming hydrostatic pore pressure on the faults, frictional coefficients between 0.10 and 0.64 are required to enable slip. On the other hand, when the frictional coefficient has been fixed to 0.65, the required pore pressure values range from 0.38 to 0.62 of lithostatic with an average of 0.48. The absolute stress magnitudes inferred from the analysis of the focal mechanisms compare favourably with the in-situ measurements of absolute stresses from the KTB borehole at Windischeschenbach (German continental deep drilling program).