This study investigated the relationship between fundamental frequency difference limens (F0DLs) and the lowest harmonic number present over a wide range of F0s (30–2000 Hz) for 12-component harmonic complex tones that were presented in either sine or random phase. For fundamental frequencies (F0s) between 100 and 400 Hz, a transition from low (∼1%) to high (∼5%) F0DLs occurred as the lowest harmonic number increased from about seven to ten, in line with earlier studies. At lower and higher F0s, the transition between low and high F0DLs occurred at lower harmonic numbers. The worsening performance at low F0s was reasonably well predicted by the expected decrease in spectral resolution below about 500 Hz. At higher F0s, the degradation in performance at lower harmonic numbers could not be predicted by changes in spectral resolution but remained relatively good (<2%–3%) in some conditions, even when all harmonics were above 8 kHz, confirming that F0 can be extracted from harmonics even when temporal envelope or fine-structure cues are weak or absent.