The aim of SIL, which was founded in 1922, is to further the study and understanding of all aspects of limnology. A primary means toward this end is through the organization of triennial congresses to promote scientific intercourse among those pursuing fundamental research and those concerned with practical fishery, pollution, and water-supply problems. Generally about a week is devoted to contributed papers and discussions and a week or longer for scientific excursions to lakes and rivers, laboratories, fishery institutions, places where pollution problems are being addressed, and water treatment facilities. Any member is entitled to give a lecture on one of a great diversity of subjects of special interest. A few authorities are invited to lecture on subjects of particular current interest and other speakers are encouraged to make contributions to selected themes of either outstanding universal topicality or of special relevance to the host country.