After placing a female house mouse into the home cage of a male, the occurrences of four behaviors were recorded on separate channels of an event recorder: (1) male sniffing female, (2) male mounting female, (3) male intromitting female, and (4) 70-kHz vocalizations. The amount of vocalizing was greatest shortly after pairing and was associated with the male sniffing the female. After the male began mounting, vocalizations also were associated with mounting. Vocalizations were recorded during intromissions and occasionally occurred coincident with pelvic thrusts. Very few vocalizations were detected when the male was not sniffing or mounting the female. Vocalizations ceased following ejaculation but typically resumed several minutes before the resumption of another mounting sequence. Thus 70-kHz vocalizations appear to be closely linked to male sexual arousal.