The low-frequency underwater hearing thresholds for pure-tone signals between 75 and 1600 Hz for an Atlantic bottlenose dolphin, a false killer whale, and a Risso's dolphin were determined using behavioral measures. All thresholds were obtained behaviorally by training the animals to station in a hoop and press a response lever when sounds were presented and to wait in the stationing position if no sound was heard. Data were collected using a staircase procedure with signals presented in 1-dB steps. Thresholds were then determined when the means for two consecutive ten reversal sessions differed by no more than 3 dB. In comparison to very sensitive hearing capabilities for these odontocete species at high frequencies, all animals showed relatively poor hearing for these lower frequencies. Most thresholds exceeded 125 dB re: 1 Pa.