This report describes the first sounds recorded from the phocoenid porpoise, vaquita, (Phocoena sinus, Norris & McFarland, 1958). High-frequency recordings were obtained near free-ranging vaquita in the northern Gulf of California in 1986 and 1987. All P. sinus clicks were sharp, intense, and narrow-band (x =17.1 + s.d. 5.38 kHz) signals that ranged in frequency from 122.2-146.9 kHz, and dominant frequencies ranging from 128.0-139.0 kHz. Click duration ranged from 79-193 μsec. Phocoena sinus acoustic signals were similar to those described for other members of the Phocoenidae as well as the distantly related delphinids,* Cephalorhynchus spp. Similarities in sound structure among these species are probably linked to the utilization of analogous habitats.