Several different factors in the collection and preservation of whale skin and blubber samples were examined to determine their effect on the results obtained by stable nitrogen and carbon isotope (δ15N and δ13C) analysis. Samples of wet killer whale skin retained their original stable isotope values for up to 14 d at 4°C or lower. However, decomposition significantly changed the δ15N value within 3 d at 20°C. Storage at −20°C was as effective as −80°C for the preservation of skin and blubber samples for stable isotope analysis for at least a year. By contrast, once a skin sample had been freeze-dried and lipid extracted, the stable isotope values did not change significantly when it was stored dry at room temperature for at least 12 mo. Preservation of whale skin samples for a month in DMSO-salt solution, frozen or at room temperature, did not significantly change the δ15N and δ13C values of lipid extracted tissues, although the slight changes seen could influence results of a study if only small changes are expected.