The role of interface strain and dipole layers in detenrining the electronic properties of two lattice matched HI-V semiconductor superlattices, InAs/AIGaAsSb and GaAs/AlAs, has been investigated with the self-consistent pseudopotential method. Values for the total energies, interface structures, valence band offsets, and charge density distributions are reported. In the InAs/AlGaAsSb system, since both the group III and V sublattices are different, large intrinsic strains are present at the interface. If the interface strain is neglected in the calculation, the valence band offset is found to be 0.05 eV, in poor agreement with the experimental value of 0.21 eV obtained from infrared photoluminescence spectroscopy. The valence band offset for the relaxed structure (obtained by minimizing the total energy with respect to atomic relaxations at the interface) is 0.24 eV, in excellent agreement with the experimental value. The interface relaxations modify the interface dipole through charge transfer between interface cation and anion. In addition to the intrinsic interface strain, the effect of extrinsic interface dipole layers, both III-V (InAs, GaSb) and group IV (Si and Ge) interlayers, has been investigated in the GaAs/AlAs lattice-matched system. The III-V interlayers are not effective in changing the band offset due to small charge asymmetry and large screening of the induced dipole. On the other hand, the group IV interlayers are found to have a dramatic effect, changing the GaAs/AlAs band offset by ∼1 eV. The group IV interlayers produce a step potential at the interface, resulting in the large offset change.