In this interview, Samuel Epstein discusses growing up in Poland and his immigration to Canada; his first interest in science and his undergraduate work at the University of Manitoba; graduate work at McGill University; work on the Canadian Atomic Energy Project; his work with Henry Thode on isotopes, using mass spectrometry; work with Harold Urey on paleotemperatures and his work with geophysicist Heinz Lowenstam; the rise of geosciences at the California Institute of Technology (Caltech) in the 1950s under Robert Sharp, and the hiring of Harrison Brown, Clair Patterson, Gerald Wasserburg. The interview concludes with comments on Linus Pauling's departure from Caltech, and reminiscences of his career and colleagues.