The social and communication signals of several species of free-ranging delphinids have been analyzed and characterized by a number of workers over the past 3 decades. Most of the past works have used bandlimited recording equipment and have focused on the sonic components of the signals. Therefore, most discussions of delphinid whistles and nonecholocation pulsed signals have been limited almost exclusively to below approximately 20 kHz. A technique has been developed that allows one to collect high-fidelity recordings of signals up to 55 kHz in frequency. By digitizing signals directly into a laptop computer through a PCMCIA A/D converter, the sonic and ultrasonic components of the whistles and burst pulses of two populations of Hawaiian spinner and spotted dolphins (Stenella longirostris and S. attenuata) resident along the leeward coast of Oahu, Hawaii are being studied. Preliminary results show that the ultrasonic range above 20 kHz is rich with whistle harmonics and components of pulsed signals.