The elongated Giuv Syenite (Aar-Massif, Switzerland) contains remarkably high amounts of thorium and uranium. Mean values of 44 samples: 66.0 p.p.m. Th, 22.1 p.p.m. U,Th/U= 3.19. U and Th have, despite the relatively small dimensions (6 × 0.5 km) of the syenite body, a zonal distribution: uranium concentrations increase from a core area with 15.0 p.p.m. towards rim zones with 28.1 p.p.m., whereas the Th/U ratio decreases from 3.68 to 2.75. This zonal arrangement corresponds roughly to the distribution of rock types in the syenite (fine-grained rim facies, porphyritic central facies). The finer-grained variety has higher values (means of 11 samples: 78.7 p.p.m. Th, 30.8 p.p.m. U,Th/U= 2.74) than the porphyritic facies (means of 33 samples: 61.8 p.p.m. Th, 19.2 p.p.m. U,Th/U= 3.35). Potassium is more or less homogeneously distributed within the syenite mass (mean of 44 determinations: 4.9% K, width of variation: 3.5–5.7% K). Anomalously high U concentrations (up to 270 p.p.m.) at shear zones are signs of postintrusive redistribution processes.