Fish fillet is a source of dietary protein with a well-balanced amino acid composition that also contains high levels of 13-vitamins and high levels of the trace elements selenium and iodide. In the present study, we elucidated whether there was a partitioning of the micro-and macronutrients between the soluble fractions (fish protein hydrolysate, FPH) and the insoluble fractions obtained after the enzymatic hydrolysis of fish-raw materials. The FPHs from cod, salmon and saithe contained high levels of taurine, potassium and 13-vitamins. Salmon FPH was particularly rich in niacin and pantothenic acid. All FPHs were low in the amino acid tryptophan. The cod and saithe insoluble peptide fractions contained high levels of the indispensable amino acids including tryptophan and of the trace elements selenium, iron and zinc. Iodide levels were high in both the soluble and insoluble fractions. Potential explanations for the segregation of macro- and micronutrients between the FPHs and their corresponding insoluble peptide fractions are discussed. These differences may have nutritional impact when testing different FPHs or insoluble peptide fractions in biological systems. (c) 2007 Elsevier Ltd. All rights reserved.