Models have been developed in Kiel for massive (Pop. I) WR stars which account for multi-level non-LTE radiation transfer in spherically expanding atmospheres. The published (Koesterke et al. 1992) grid of models for WC composition (40% helium, 60% carbon by mass) can be applied to low-mass stars as well by means of the scaling properties of WR spectra (Hamann et al. 1992) and allow a rough guess of the parameters, while individual calculations are necessary for a detailed analysis and the determination of the chemical composition.