An alarming situation exists in the arid regions of central Asia and elsewhere, where increase of population and industry has resulted in overuse of the natural water supply. Ambitious measures proposed in the Soviet Union for solving this problem by diverting water from the rivers which flow into the Arctic Ocean are outlined from published information and are seen to raise novel questions, arising from possible unintended and undesirable side-effects on the distribution of climates over many parts of the Northern Hemisphere. The importance of informed scientific study and discussion of the meteorological problem, using a variety of techniques and taking account of the history of natural climatic fluctuations, as well as the margins of error likely in any attempted predictions, is stressed."