Critical bands (CBs) were measured in the parakeet by obtaining masked thresholds for a pure tone in the presence of noise bands of varying bandwidth. Six test frequencies were used and masked thresholds were estimated for between six and eight bands of noise at each. The CB was determined as the intersection of two regression lines fitted to the masked thresholds; one for those thresholds that were independent of masker bandwidth and the second for those thresholds which were dependent on masker bandwidth (Fig. 2). The critical band was similar to that reported in other species in that it was consistently greater than the critical ratio by about 2.5–3.0 times. The value of the CB at various test frequencies tends to increase at a rate of 3 dB per octave in many other species. In the parakeet however, the size of the CB is relatively constant between 0.25 and 4.0 kHz and then rapidly increases. The unusual shape of the critical band curve suggests that there may be a unique organization of the internal auditory filters that are associated with the CB in this species.