The biotic succession of the Sverdrup Basin, Canadian Arctic, records a significant Permian climatic cooling trend. Highly diversified, tropicallike associations dominated by calcareous alga and foraminifer (Chloroforam) prevailed during the Asselian and Sakmarian, whereas poorly diversified, temperatelike associations, dominated by bryozoan, echinoderm, and brachiopod, characterized the Artinskian (Bryonoderm-extended) to Kazanian (Bryonoderm) interval. Polarlike, siliceous sponge–dominated biota (Hyalosponge) prevailed during the latest Permian. The climatic gradient suggested by this trend, and by other climatic indicators (ooid, oncoid, evaporite, reef, submarine cement, dropstone, red bed, caliche, coal), is far greater than that expected from the 10 to 15° of northerly migration inferred for Pangea during the Permian. The cooling trend, the causes of which are unknown, is evidence for a dramatic climatic deterioration in northern Pangea at the end of the Paleozoic.