We investigated the structural, elastic and electronic properties of a series of early transition metal carbides and nitrides, namely, those formed with 3d metals (TiC, TiN), 4d metals (ZrC, NbC and 5d metals (HfC, HfN), and their ternary alloys. The calculation are based on accurate first-principles total-energy calculations using the hybrid full-potential augmented plane-wave plus local orbitals method. We have used the local-density as well as the generalized gradient approximations for the exchange and correlation potential. The ground state properties, equilibrium lattice constants, bulk moduli, elastic constants and the charge densities are determined for both the binary and their related ternary alloys. The densities of electron states for TiCxN1-x ZrxNb1-xC and HfCxN1-x alloys are also presented. A model structure of sixteen-atom supercell is used. (C) 2004 Elsevier B.V. All rights reserved.