Auditory thresholds in the presence of masking noise and masking tones were measured in three species of teleost fishes: goldfish (Carassius auratus, family Cyprinidae); pin fish (Lagodon rhomboides, family Sparidae); African mouth-Breeder (Tilapia macrocephala, family Cichlidae). In the goldfish, the signal-to-noise ratio to broad-band noise was about 22 dB, and direct measurement of the critical band yielded a value between 100 and 200 Hz. Single-tone masking effects in the goldfish showed partial remote masking, and strong masking at frequencies within 5 to 20 Hz of the signal. The audiograms for pinfish and Tilapia were significantly higher than in the goldfish, but the signal-to-noise ratio values were in the same range. Provisionally, the evidence supports the existence of a critical band in the goldfish, but not in the other species tested. The question of the relationship of signal-to-noise ratio to the critical band was discussed in reference to the frequency-discrimination capacities and hearing mechanisms in fishes.