This research combines experimental and theoretical approaches to investigate mechanisms of slip transmission across coherent interphase boundaries in intermetallic compounds. Single crystal titanium aluminides, TiAl and Ti3Al, are grown, mechanically tested, and the results compared to theoretical predictions of dislocation core structures and the interaction of dislocations with interphase boundaries. Computer modeling of the interface between the aluminide phases is carried out in parallel with the dislocation calculations. The microstructures of the alloys are varied by combinations of diffusion bonding and/or diffusive infiltration. The fracture mechanisms in these intermetallic materials are assessed. Compression testing, transmission electron microscopy, and atomic force microscopy are employed. %%% This research advances the frontiers of atomistic modeling for simulating interfaces and understanding of mechanical behavior in high temperature intermetallic alloys of technological importance.