Radiochemical procedures are described for the determination of iron 55Fe and nickel 63Ni isotopes in environmental samples. The methods were based on the mineralisation of sediment and biological material, coprecipitation and separation of iron and nickel on anion exchange resin. The separated isotopes were electroplated onto a copper disc and their activi-ties was measured by beta spectrometry using an anti-coincidence GM gas flow counter. The proposed procedures were tested on samples from the Baltic Sea. The concentration of 55Fe in reactor water samples falls within the range from 0.15 to 2185 Bq ?1-1,while in brown algae Fucus vesiculosus it lies between 0.13 and 3.50 Bq ? kg-1 dry wt. The 63Ni is non-uniformly distributed within the Baltic fish. More than 95% of the total 63Ni content in cod and herring is located in fillet with skin and scale.