Temporal integration of loudness for 1-kHz tones and broadband noises was compared over a wide range of levels. Absolute thresholds and levels required to produce equal loudness were measured for 5-, 30-, and 200-ms stimuli using an adaptive, two-interval, two-alternative forced-choice procedure. Levels ranged from 5 to 80 dB SL for noises and from 5 to 90 dB SL for tones. Results for six listeners with normal hearing show that the amount of temporal integration, defined as the level difference between equally loud 5- and 200-ms stimuli, varies nonmonotonically with level. The average amount of temporal integration varies from about 10-12 dB near threshold, to a peak of 18-19 dB when the 5-ms tone is about 56 dB and the 5-ms noise is about 76 dB SPL; the amount of temporal integration decreases to 10 dB for tones and 13 dB for noises with levels around 100 dB SPL. The data for tones are in good agreement with the majority of existing data. The data for noises are within the range of the few previous data, but the effect of level differs from that obtained in previous studies. The present results indicate that the growth of loudness may, at least in part, be consistent with the nonlinear input/output function of the basilar membrane.