Numerous theoretical efforts have been developed to identify molecular-morphological relationships in ordered AB diblock copolymers, but relatively few, studies have sought to elucidate similar relationships in blends composed of two strongly segregated diblock copolymers, (AB)(alpha) and (AB)(beta). Since block mixing occurs at the molecular level in miscible (AB)(alpha)/(AB)(beta) blends, relatively precise control over morphological development and microstructural dimensions can be achieved without the need to synthesize tailored materials; With the junctions of the alpha and beta copolymer molecules. confined to interphase regions at equilibrium in the strong-segregation regime, (AB)(alpha)/(AB)(beta) blends may be envisioned as a bidisperse mixture of grafted chains and prove more well-behaved than copolymer/homopolymer blends.;In this work, a self-consistent field theory is proposed for binary diblock copolymer-blends possessing the lamellar morphology. Analytical expressions and corresponding predictions for the free energy and microdomain periodicity are provided for-blends in;which the constituent copolymers differ in composition and-chain length. Predicted blend periodicities are in quantitative agreement with recent experimental results.