Ab initio electronic structure calculations of hypothetical zinc-blende CaX (X = P, As, Sb) were performed using tight-binding linear muffin-tin orbital method. It was found that, these compounds are ferromagnets exhibiting half-metallicity. Total energy calculations show that the zinc blende ferromagnetic phase is more stable than the zinc-blende non-magnetic phase at equilibrium volume. Ground state properties such as equilibrium lattice constant, bulk modulus and cohesive energy were calculated. The calculated magnetic moment is found to be μB per formula unit for all these materials, which agrees well with the other theoretical results. On reducing the cell volume all these compounds are found to undergo a magnetic phase transition from zinc-blende ferromagnetic phase to zinc-blende non-magnetic phase. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.