Researchers describe Mandarin Chinese tone phonemes by their fundamental frequency (Fo) contours. However, tone phonemes are also comprised of higher harmonics that also may cue tone phonemes. We measured identification thresholds of acoustically filtered tone phonemes and found that higher harmonics, including resolved harmonics above the Fo and unresolved harmonics, cued tone phonemes. Resolved harmonics cued tone phonemes at lower intensity levels suggesting they are more practical tone-phoneme cues in everyday speech. The clear implication is that researchers should use the Fo only as a benchmark when describing tone-phoneme contours, recognizing that higher harmonics also cue tone phonemes. These results also help explain why tone-language speakers can identify tone phonemes over a telephone that attenuates selective frequencies, and suggests that hearing-impaired tone-language speakers may still identify tone phonemes when their hearing loss attenuates selective frequencies.