Since 1997, the North-east inter-regional delegation of the French National Institute for Water and Aquatic Ecosystems (ONEMA) has been running annual networked monitoring of the great cormorant (Phalacrocorax carbo sinensis) population in three French administrative regions: Alsace, Lorraine and Champagne-Ardenne. Changes in the wintering population are assessed by means of four monthly counts. Over the period 1997/2001, the population increased at a steady rate (average annual increase of 16%). Taking the population in January as the reference, the year 2001 shows a peak population of 13 000 birds. Since 2002, gradual decreasing in numbers has taken place (average rate of –4.5%). In January 2008, less than 10 000 birds were recorded. At the same time, nesting of the great cormorant was observed for the first time in Lorraine region in 1986. Then, the bird has been nesting in Champagne-Ardenne region and, since 2003, in all three regions. In 2008, ten nesting colonies were identified, composed of 512 couples (annual increase in population of 30.2%) and 1500 births were recorded in Spring. Parallel to nesting, 4605 great cormorants were killed during the winter of 2007/2008 for a population of 10 000 birds. Climatic conditions may cause significant changes in wintering movements of the species, while operations to regulate cormorant numbers do not seem to have significant impact on the level of frequentation in winter. Finally, the using conditions of certain artificial lakes seem to be favourable for the bird during particularly difficult periods.