The determination of the abundances of stars from their high resolution spectra forms the most fundamental observational basis for understanding how stars evolve through their life cycles. The Principal Investigator (PI) will continue his previous NSF- supported work to determine to what extent interior nuclear reactions are responsible for the creation of heavy elements, which subsequently alter the chemical composition of interstellar gas via stellar mass loss and influence the evolution of future generations of stars. The PI's new work will focus both on the chemical composition of stars in our own Galaxy and in those of the Magellanic Clouds in the Southern hemisphere. In addition to concentrating on the production of certain heavy elements (Ge, Rb, and Mo), the PI will concentrate on 13C, the light-metals abundances in massive stars, Li abundance in solar-type stars, and the apparent chemical anomalies in chemically peculiar A stars known as "lambda Bootis" stars. In addition to clarifying the role of networks of heavy-element nuclear reactions in stellar cores, this research is expected to help our understanding of the possible roles of convective mixing and radiative diffusion in the envelopes of many stars on the "main sequence."