Org. exts. and kerogens of 43 core samples from the Molasse Basin of southern Germany were investigated with respect to their 13C-12C isotope compn. and the 34S-32S and 15N-14N isotope distributions of 13 samples of crude oil. According to 34S detns., all crude oils from the Tertiary of the western and eastern Molasse belong to one single oil family; they differ significantly from the Triasic and Lias oils of the western Molasse. The oils of Tettnang, Aitingen, and Hofolding are assocd. with the group of oils from the Tertiary. An enrichment of 34S was obsd. in crude oil fractions with increasing polarity. The isotope distributions of S in the polar constituents of the biodegraded oils from the sandstones of Ampfing, however, approach a homogeneous distribution. From oil-source rock correlation by 13C detns., the Sannoisian Fischschiefer formation may be regarded as a potential source rock of the Terhary oils. In addn., an influence of the Upper Cretaceous cannot be excluded in the eastern Molasse. The distribution of the N isotopes was to be very uniform in southern German oils, and a regional differentiation cannot be recognized. The 15N values of the crudes do not show any systematic correlation with those of their sepd. asphaltenes.