A new multiband formalism for the semiempirical calculation of deep-level wave functions in k space is presented. This approach is based upon the Hjalmarson et al. theory of deep levels in semiconductors and is an extension to k space of the real-space wave-function theory of Ren et al. Wave functions of A1 symmetry associated with GaP:N and with a level at 1.65 eV above the GaP valence band are calculated and compared with the results of Jaros for the same cases. These calculations demonstrate that this formalism can be used for calculating multiband deep-level wave functions in k space.