Summer and winter crude oil spills have been made on tundra and taiga sites in arctic Canada. The short- and long-term effects of these spills have been recorded, to date, over a 3-year period. Spills were made by even surface spraying and by high intensity point spills. The vegetation present prior to such spills was carefully recorded. All surface spills had a devastating effect on above-ground vegetation. Species did, however, differ markedly in both their ability to survive an oil spill and their ability to recover. Many species, especially lichens, mosses, and liverworts, were killed outright. Some woody and dwarf shrubs were able to produce new, healthy shoots within a few weeks of initial defoliation. The reduced production of storage material, as a result of foliage (and photosynthetic) loss, caused markedly increased plant losses by winter-killing factors. Flowering and reproduction were severely reduced, even in the third summer following a spill. Winter spills had significantly less effect than summer spills. Permafrost was little affected, despite changes in the site energy budgets. Damage appeared greater in exposed taiga sites than on the tundra. Some species, such as black spruce, died throughout a 3-year period, emphasizing the necessity for long-term studies for accurate assessment.