This report is a contribution to the Strategic Environmental Assessment (SEA3) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). The report is a synthesis of information on human activities which might have an impact on, or themselves be affected by, further oil and gas developments in the SEA3 area of the North Sea. The activities include shipping, energy (both existing oil and gas developments and renewable energy), telecommunications, military activities, waste disposal, dredging and aggregate extraction, marine archaeological sites and wrecks. The SEA3 area hosts a wide variety of different users. Some have been there for centuries, others are more recent arrivals. Among the older industries and activities are fisheries, ports and shipping, military activities and sea bathing. The offshore oil and gas industry has developed into a major player in the North Sea since the late 1960s, with considerable infrastructure of pipelines and coastal gas terminals in the SEA3 area. The number of submarine telecommunication cables across the North Sea has grown enormously in the past ten years, with the advent of the fibre optic cable and the growth of the Internet and e-commerce. The next twenty years may see considerable development of offshore wind farms in the SEA3 area.