In this study we have analyzed the incidence, range, frequency spectrum and threshold of distortion products in a sample of 232 normal hearing person. 116 younger adults, 58 female ranging in age from 18 to 30 years (mean age 23.1) and 58 males ranging in age from 18 to 32 (mean age 23.7) were included in the study. In all the ears studied, the presence of distortion products in a normal ear were found with regularity in the frequency region between 700 to 6,000 Hz. Higher incidence occurred in younger people and women but was not statistically notable. There is a direct correlation between distortion products amplitude and its primary intensity. Distortion products amplitude increases progressively from low (770 Hz) to high frequencies (6,000 Hz). The amplitude of distortion products and its mean value is higher in women, in all frequencies, except in the 700 to 1,000 Hz region. Input/output function had a mean of 50 dB SPL at 1 kHz, 43.8 at 2 kHz, 38.4 at 4 kHz and 33.5 at 6 kHz.