Discrimination of envelope frequency was measured as the just noticeable increase in envelope frequency of monotic, 60‐dB two‐tone complexes at geometric center frequencies (CFs) of 500, 1000, 2000, and 4000 Hz. (The envelope frequency is equal to the frequency separation ΔF, between the two components.) At a given CF the jnds were approximately constant up to a critical envelope frequency between 10% and 20% of the CF, roughly equivalent to the critical band, beyond which they increased to a maximum at about 40% of the CF. Below the critical envelope frequency, the jnd increased with CF. Measurements at 40 dB SPL with and without masking of the aural distortion products showed that the influence of aural distortion is minimal. Additional measurements showed that at narrow frequency separations, discrimination was better for monotic two‐tone complexes than for pure tones, three‐tone complexes, and dichotic two‐tone complexes. The results indicate that envelope frequency may serve as a cue for discrimination up to a frequency between 30% and 40% of the CF, although its effectiveness at high enevelope frequencies is severely diminished by the auditory filter. A comparison with other data on envelope frequency discrimination indicates that the jnds’ dependence on the envelope frequency may depend on how the slope of the temporal envelope varies with envelope frequency.