Echolocation calls were recorded from Pteronotus quadridens flying in the field and in an enclosed space. In the field, search calls contained 1 or 2 harmonics. Patterns of call design show a segment of quasi–constant frequency (QCF_2nd-harmonic at 81–84 kHz), followed by a downward frequency-modulated (FM) component. The 2nd harmonic was always more intense than the 1st. Search, approach, and terminal phases of calls were described during hunting sequences of P. quadridens. The transition between call phases was characterized by monotonic variations in some acoustic parameters, including a decrease in call duration and an increase in repetition rate, bandwidth, and slope of the FM component. We also analyzed calls emitted by bats flying in confined spaces that consistently contained 3 harmonics, of which the 2nd harmonic contained the greatest energy. The values of call duration were shorter and bandwidth was higher than values characterizing calls emitted during the search phase in the field.