Calls at frequencies below the range of human hearing were recorded from two groups of captive Asian elephants (Elephas maximus). Most of the calls ranged in frequency from 14 to 24 Hz, with durations of 10–15 s (Fig. 1). With the nearest elephant 5 m from the microphone, sound pressure levels were 85 to 90 dB (re 20 μPa). These calls occurred in a variety of circumstances. Elephants are the first terrestrial mammals reported to produce infrasound. These calls may be important in the coordination of behavior in thick vegetation or among separated groups of elephants.