Lake Päijänne Symposium. Jyväskylä (Finland), March 19-20, 1987. The first Symposium on Lake Päijänne was arranged during the 150th anniversary of the City of Jyväskylä and its protector was Mr. Matti Ahde, Minister for the Environment. The meeting was arranged by the Departments of Biology and Chemistry and by the Institute for Environmental Research at the University of Jyväskylä. Financial support for the arrangements was received from the Academy of Finland, University of Jyvaskyla, City of Jyväskylä, Merck Ltd., Millipore and the Savings Bank of Central Finland. About 120 persons participated in the symposium, and the program consisted of 26 lectures and 9 posters. Most of the original papers have been collected in this publication.