Evolution of C/N/O abundances for different masses (from left to right panels: 60, 40, ~30, 25, and 20 M_⊙) as a functionof T_eff, as predicted by the rotating Geneva (black lines, left panels) and Bonn tracks (red lines, right panels). The dotted line represents the solar abundance. The dashed and the dash-dotted lines display the initial abundances used in the Geneva andin the Bonn calculations, respectively. Our results (symbols as in Fig. 1) are shown with errors accounting for typical uncertainties in stellar parameters. For initial evolutionary masses of sample stars, see Table 5.