Enrichment of the heaviest elements Th and Pb in the Galaxy

The heaviest elements Th and Pb are key to understanding the neutron-capture reactions in the Universe. Abundance measurements of these elements for metal-deficient stars in the past dacade provide useful constraints on both the r- and s-processes, and early chemical enrichment in the Galaxy. Recent observational results on abundance ratios of Th to other stable elements in metal-deficient stars, Pb production of both r- and s-processes, and their enrichment history in the Galaxy are reviewed.