13C- and 1H-ENDOR studies on a phenoxyl type radical in fluid solution are reported. The 13C-ENDOR resonance lines are comparable with those of the protons concerning amplitude, linewidth, and optimum experimental conditions. These findings are in contrast to previous ENDOR experiments on other 13C-labelled systems and can be explained by assuming similar hfs anisotropies for carbon-13 and protons in this radical. From saturation measurements the relaxation parameters were determined. The hyperfine couplings are discussed in terms of McLachlan and INDO calculations. For the first time natural abundance 13C-ENDOR measurements have been successful.