[en] The present document is the seventeenth report published by the Health and Safety Directorate of the Commission of the European Communities concerning ambient radioactivity. It was drawn up using the data collected by the stations responsible for environmental radioactivity monitoring in the Member States. The results are extracts from the data sent to the Commission in application of Article 36 of the Treaty of Rome establishing the European Atomic Energy Community. The results presented in this report deal with radioactive contamination of the air, precipitation and fallout, surface water and milk during 1977 in the nine Member States of the European Community, viz. Belgium, Denmark, the Federal Republic of Germany, France, Italy, Ireland, Luxembourg, the Netherlands and the United Kingdom. The report also contains supplementary data on short-lived radioelements detected during the fourth quarter of 1977, the list of sampling stations and laboratories together With a list of publications by Member States in this field. This report places special emphasis on the measurement results for specific radionuclides, but it also contains data on total beta activity so as to ensure continuity vis-a-vis previous reports and provide comparative values