This study presents a unique procedure for determining the critical duration and temporal summation function. With this procedure, duration as a parameter was used to determine the temporal summation characteristics of ten normal ears. An apparatus was constructed that permitted subjects to track threshold by modulating the burst width of a brief tonal stimulus. The apparatus permitted experimenter control of the rate of burst width modulation and interburst interval. The burst width could be continuously varied by the subject from 10 to 800 msec. Asymptotic regression indicated that the data were best fit to a simple power function of the form Y = AX(B). A logarithmic transformation was applied to the obtained durations, and slopes of integration were determined for each frequency. These values ranged between 6.3 and 10.2 dB/log unit time. Differences among frequencies were found to be significant. Critical durations were obtained for each subject, and these values were consistent with previous data indicating negligible temporal summation about 150 to 200 msec.