The electronic structure of the blue bronze A0.30MoO3(A = K, Rb) was examined by performing tight-binding band calculations on a number of model chains and an Moi0O30slab. When normalized to A3Mo10O30(i.e., half the unit cell), the bottom two d-block bands of an Mo10O30slab are partially filled. The Fermi surfaces of these two bands are open along the interchain direction, in agreement with the experimental fact that the blue bronze is a pseudo-one-dimensional metal with good electrical conductivity along the chain direction b. The Fermi surfaces of the two bands are curved due to interactions between adjacent Mo10O32chains, but the curvatures of the Fermi surfaces are opposite for the two bands. Thus the two pieces of the first-band Fermi surface are nested to those of the second-band Fermi surface by a single wave vector qb≃ 0.75b*, which explains why only one charge density wave occurs in the blue bronze. For an Mo10O30slab, the bottom of the third d-block band is calculated to lie above, but very close to, the Fermi level (i.e., 0.012 eV above ef). This feature is responsible for the temperature dependence of qbin the blue bronze, which increases gradually from-0.72b* at room temperature to-0.75b* below the metal-to-semiconductor phase-transition temperature.