The nucleosynthetic origin of the galactic cosmic-ray sources (GCRS) is a matter of same considerable interest (e.g., Leske; Connell & Simpson; DuVernois et al.). Any understanding of this origin requires an accurate determination of the source elemental abundances. These abundances are determined by comparing the Ulysses High-Energy Telescope (HET) observations in the heliosphere, made at an average energy of 185 MeV nucleon, and a solar modulation level of Phi = 750 MV, with results of interstellar propagation calculations. We also incorporate the HEAO 3 C-2 elemental measurements into our determinations. By comparing the data with propagated trial-source abundances, we derive, subject to the parameters of our propagation algorithm, the best-fit source elemental abundances.