Lichens of the most highly stressful habitats in Sverdrup Pass, Ellesmere Island, Northwest Territories, Canada, were examined for reproductive structures, as were lichens of less extreme sites within the same landform features. The study areas included twenty-two stands in a calcareous erosional mountain system and two microhabitats within the ablation zone of a valley glacier. In the most limited stands in the erosional mountains 83% of the lichens were apotheciate species and 93% of these were represented by specimens bearing apothecia. On stressful rock surfaces in the glacier fellfield most species also produced sexual fruiting bodies.