Metallicity gradient in the disk of the Milky Way. Plotted are data for (1) old open clusters from Twarog et al. (1997) and from Chen et al. (2003) as diamonds and Yong et al. (2005) as squares, (2) field red giants (Carney et al. 2005) as circles, and (3) Cepheids from Andrievsky et al. (2002a, 2002b), Luck et al. (2003), and Andrievsky et al. (2004) as crosses. The discrepancy is obvious between old star abundances (diamonds, squares, and crossed) and Cepheids (crosses) in the region 10–15 kpc.