To suppress interdiffusion between the coating and alloy substrate in addition to ensuring slow oxide growth at very high temperatures advanced coatings were developed, and they were classified into four groups, (1) the diffusion barrier coating with a duplex layer structure, an inner sigma-(Re-Cr-Ni) phase as a diffusion barrier and outer Ni aluminides as an aluminum reservoir formed on a Ni based superalloy, Hastelloy X, and Nb-based alloy. (2) the up-hill diffusion coating with a duplex layer structure, an inner TiAl(2) + Ll(2) and an outer beta-NiAl formed on TiAl intermetallic and Ti-based heat resistant alloys by the Ni-plating followed by high Al-activity pack cementation. (3) the chemical barrier coating with a duplex layer structure, an inner gamma + beta + Laves three phases mixture as a chemical diffusion banier and an outer Al-rich gamma-TiAl as an Al reservoir formed by the two step Cr/Al pack process. (4) the self-formed coating with the duplex structure, an inner alpha-Cr layer as a diffusion barrier and an outer beta-NiAl as an Al-reservoir on Ni-(20 similar to 50)at% Cr alloy changed from the delta-Ni(2)Al(3) coating during oxidation at high temperature. The oxidation properties of the coated alloys were investigated at temperatures between 1173 and 1573K in air for up to 1,000 hrs (10,000 hrs for the up-hill diffusion coating). In the diffusion barrier coating the Re-Cr-Ni alloy layer was stable, existing between the Ni-based superalloy (or Hastelloy X) and Ni aluminides containing 12 similar to 50at%Al when oxidized at 1423K for up to 1800ks. It was found that the Re-Cr-Ni alloy layer acts as a diffusion barrier for both the inward diffusion of Al and outward diffusion of alloying elements in the ahoy substrate. In the chemical barrier coating both the TiAl(2) outermost and Al-rich gamma-TiAl outer layers maintained high Al contents, forming a protective Al(2)O(3) scale, and it seems that the inner, gamma, beta, Laves three phase mixture layer suppresses mutual diffusion between the alloy substrate and the outer/outermost layers.