Stoichiometric TiNi and its alloys containing Cu or excess Ni were measured to study the lattice component of the thermal conductivity. The low‐temperature phonon mean‐free‐path is constant, depends upon solute species, and increases with solute concentration. In addition, the ideal component of the electrical resistivity shows theT2dependence below 100°K found for the element and alloys with this same electron number. Values of the Fermi energy, effective mass, and the relative valence of the solutes are derived. Finally, one of the alloyed samples exhibits phase changes which are believed related to those seen in the pure material at temperatures above 300°K.