Recent ground temperature and observational data for lithalsas in the subarctic Canadian Shield (permafrost mounds of ice-rich, fine-grained sediments) are examined in the context of an inventory of thermokarst ponding between 1945 and 2005. Results show that many lithalsas are thermally and physically degrading, and widespread thermokarst primarily relates to lithalsa distribution. Future thermokarst development in this region of extensive discontinuous permafrost will continue to be associated with lithalsas that often lack a protective surface organic layer.