Abstract The experimental relation between the superconducting transition temperature ( T c) and lattice size for the lanthanide nickel borocarbides is clarified. The electronic density of states (DOS) at the Fermi energy is calculated by the LMTO method for selected non-magnetic lanthanides. The T c and the DOS are both shown to scale in the same way with a structural parameter that characterizes the bond angle in the NiB 4 tetrahedra. The results strongly support arguments that the suppression of superconductivity on going from smaller to larger lanthanides in the quaternary nickel borocarbides is structurally driven. A structure– T c relationship of this type is unusual for intermetallic superconductors.