Maple dieback, a disease condition of unknown etiology affecting sugar maple and other hardwoods in woodlots, was studied over a 6-year period to determine its severity and extent. Data from permanent sample plots showed a consistent recovery trend during this period among moderately affected maple and other hardwood species. Severely affected trees did not recover. Dieback did not spread to new areas. The condition was not associated with either fungous pathogens or insect pests. Adverse environmental factors are postulated as important contributing casual agents.