We have grown epitaxial NiMnSb(0 0 1) films on GaAs(0 0 1). NiMnSb is a half-metallic ferromagnet and a possible candidate for spin injection applications. Films grown at a Sb:Ni flux ratio phi (Sb):phi (Ni) = 7:1 have the best crystal quality and surface morphology, but show a Mn deficiency of similar to 20 at% and a reduced magnetization. Stoichiometric films show the highest magnetization and are obtained at phi (Sb):phi (Ni) = 10:1 The implication of thc twofold in-plane magnetic anisotropy, dependent on the growth conditions, on the interface structure and the spin polarization at the bottom NiMnSb surface will need further attention.