The Permian-Triassic (P-T) boundary is marked by the most severe mass extinction in the geologic record. High-resolution cyclostratigraphy on a 104 yr scale across the P-T boundary in a core from the Carnic Alps (Austria) revealed significant cycles in the ratio ̃40:10:4.7:2.3 m, identified with Milankovitch cycles of ̃412:100:40:20 k.y. (eccentricity 1 and 2, obliquity, and precession). Wavelet analysis indicates continuity of deposition across the boundary, with an average accumulation rate of ̃10 cm/k.y. The dramatic faunal changes at the P-T boundary can be constrained within an interval of <60 k.y. (possibly <8 k.y.), with the accompanying sharp negative global carbon-isotope shift within <30 k.y., suggesting a catastrophic cause.