Extracts and enzymic hydrolysates were prepared from cod, haddock, salmon, whale, seal, beef and pork livers. Extraction was carried out with water at pH 5; enzymic hydrolysis was effected by papain at pH 5.5 and at 65 °C. followed by pancreatin at pH 7.5 and at 50 °c. The proper digestion times were established. Extracts, as well as hydrolysates, were concentrated by distillation in vacuo to the consistency of syrup and then dried at a low temperature in vacuo. The preparations were analysed for a large number of inorganic and organic constituents. Comparisons of the results for preparations from fish livers with corresponding products from mammalian livers lead to the conclusion that fish livers are useful raw materials for the production of extracts and enzymic hydrolysates for use in foods or in medicinal preparations.