The need to gather available data on the Eurasien huchen - an important salmonid species - has been forced by a plain and, unfortunately, common fact of our times: the numbers and distribution of this biggest of salmonids have begun to decline and its range has begun to shrink. A seminar on the huchen - the European form of the species Hucha hucha - held in Zilina in February 1973 as a result of a suggestion of the Section for the Conservation of Fauna of the Slovak Zoological Society, indicated very clearly the sad situation. Data on the biology of the huchen are regrettably scarce despite several recent papers (Ivaska 1951, Svetina 1962, Prawochenski and Kolder 1968) with the aim of filling this gap. Supposing that without a thorough kwledge it is practically impossible to conserve any plant or animal species, the participants of the seminar concluded that the existing kwledge on the huchen should be compiled in an exhaustive mograph. The first such outline originated in 1977 under the authorship of J. Holcik, K. Hensel and L. Skacel, and was submitted as a research report to some of the central authorities. Even during the compilation of the report it became evident, however, that there is difference between the huchen and its relative, the taimen. Consequently, we immediately began revising our first report, which took over three years.