Average discharge rate of single auditory‐nerve fibers in cats was measured in response to one‐ and two‐tone stimuli. One component (the ’’suppressor tone’’) of each two‐tone stimulus was at a frequency (f 2) which produced two‐tone suppression at some stimulus levels. The other component (excitor tone) produced an increase in rate above the spontaneous rate when presented alone. Fractional response was defined as the driven rate to the two‐tone stimulus divided by the driven rate to the excitor alone. Fractional response is thus a quantitative measure of the amount of suppression produced by a suppressor tone. A number of qualitative differences were found in the dependence of fractional response for f 2≳CF and f 2<CF. For suppressor tone frequencies greater than CF, fractional response depends only on the ratio of suppressor to excitor levels (P 2/P 1) for a range of excitor levels (P 1). For P 1 large enough to drive a unit into saturation, fractional response increases with P 1. For f 2<CF, however, fractional response is a monotonic decreasing function of P 2 and P 2/P 1; it is also a monotonic decreasing function of P 1 for P 2/P 1 fixed. Consistent with these results if the tone level ratio P 2/P 1 is fixed, rate is a monotonic increasing function of the overall level of a two‐tone stimulus for f 2≳CF; for f 2<CF, rate is typically a nonmonotonic function of overall level. For f 2≳CF, slopes of (log) fractional response versus (log) P 2/P 1 curves are a monotonic decreasing function of suppressor frequency f 2. For f 2<CF, on the other hand, slope does not depend on f 2. If f 2 is fixed, and excitor‐tone frequency (f 1) varied, fractional response decreases with f 1 for f 2≳CF; for f 2<CF, fractional response is independent of f 1. Subject Classification: [43]65.42, [43]65.59.