The complete evolution of a star with an initial mass of 60 M⊙ and Z = Z⊙ (i.e. a typical W R progenitor) from the ZAMS through the supernova phase has been investigated. Mass loss in the different evolutionary stages, especially mass dependent W R mass loss, leads to a WO star (surface mass fractions {He,C,O} = {0.14, 0.38, 0.48}; cf. Fig. 1) of 4 . 2 M⊙ as pre-SN configuration. The low final mass may be typical for a wide range of initial masses (cf. Langer, 1989, Astr. Ap. 220, 135).