Abstract Permafrost features indicate certain upper limits for annual air and ground temperatures, with the air temperatures being usually the lower because of insulating snow and vegetation. The following features generally imply mean annual air temperatures no higher than those indicated and commonly lower: permafrost itself, large sorted forms of patterned ground, palsas, and rock glaciers, 0°C; ice-wedge polygons and well-developed soil-wedge polygons, −5°C; open-system pingos, −2°C; closed system pingos, −6°C; the implication of cryoplanation terraces remains to be established, with estimates ranging from near 0° to −12°C. Use of fossil permafrost features as temperature indicators is complicated by problems of correct identification and dating, soil type, and local and regional environmental variables such as precipitation and vegetation. Nevertheless the fact that certain maximum paleotemperatures can be reasonably established in places warrants expanded research in former periglacial areas to evaluate temperature increases to the present. The majority of determinations in Europe, where most of the work has been done to date, indicate minimum air temperature increases of 13°–18° since the maximum of the last glaciation.