Understanding of any age-related differences in distortion product otoacoustic emissions (DPOAEs) during infancy is important for the use of DPOAEs in detection of cochlear impairment in infants. We studied DPOAEs at 10 frequencies of f2 primary tone between 500 Hz to 10 kHz longitudinally during the first year of life in 70 ears of 35 normal term infants. On days 3-5 after birth DPOAE pass rates ranged between the highest 98.6% at f2 frequencies 6-10 kHz and the lowest 22.9% at 750 Hz. The higher the frequency, the higher was the pass rate. At 6 months the pass rates at various frequencies were generally similar to those on days 3-5, and were greater than 91% across the frequencies of 3-10 kHz. At 12 months the pass rates were 100% or near 100% across 3-10 kHz. During the first year the pass rate was always very low at 750 Hz (<40%) and tended to decrease at 1 kHz with the increase in age. DPOAE level at f2 frequencies 4kHz increased from birth to 6 months but then reduced slightly at 12 months. At lower frequencies the age-related DPOAE levels change was less significant. These results indicate that there are no major changes in DPOAE or cochlear function during the first year of life at most frequencies. However, the interpretation of DPOAE results in infants need to take into account the age-related difference in DPOAE pass rate at low-frequency and in DPOAE level at high-frequency.