Decrement in ABR wave V amplitude was measured in the presence of simultaneous tonal maskers. Probe stimuli were 1.0, 4.0, and 8.0‐kHz third‐octave‐filtered clicks. Adults and 3‐month‐old infants served as subjects. The resultant amplitude‐decrement functions for each tonal masker were fit with regression lines. The sound pressure level (SPL) required to reduce wave V to 50% of the unmasked probe amplitude was plotted for each masker to develop tuning curves. The tuning curves were quantified by calculations of tip‐to‐tail difference,Q10, and SPL at maximum masker frequency (MMF). Tuning curves for adult and infant subjects were similar for the 1.0‐kHz probe. For the high‐frequency probes (4.0 and 8.0 kHz), smaller tip‐to‐tail differences and lowerQ10 values were observed for the infant subjects. Ranges of MMF level were similar across adult and infant subjects. For the 8.0‐kHz probe, tuning curves from infant subjects consistently showed maximum masker frequencies which were lower than the probe.