With an increase of temperature in a stellar core in which helium has been consumed completely, various thermonuclear reactions occur successively: C12 + C12 reactions occur at 6 × 108 °K, Ne20 (γ, α)O16 reactions occur at 1.0 × 109 °K and O16 + O16 reactions occur at 1.25×109 °K. These reactions are accompanied by production and absorption of protons and α-particles, and various elements are synthesized. In the cases of C12 + C12 and O16 + O16 reactions, neutrons are also produced. If the stellar core is rich in carbon after helium burning, a considerable amount of heavy metals are produced, but if the core is rich in oxygen, heavy metals are scarecely produced. The elements remaining after oxygen burning are Mg24, Mg25, Si28, P31, etc., if carbon is abundant initially, and Si28, S32, etc., if oxygen is abundant. Reactions next arising are Mg25 (γ, n), P31(γ, p), S32(γ, p), S32(γ, α), etc., at 1.5 × 109 °K. Further, Mg24 and Si28 are disintegrated at 2 × 109 °K and then thermal equilibrium will be established for the concentrations of the disintegration products.