Mouse pups that are separated from the nest and exposed to cold temperature emit ultrasonic calls. These signals are perceived by conspecifics and play an important communicative role in mother-offspring interaction. Newborn mice are able to modify ultrasonic calls in response to different olfactory cues. Three-day-old CBA-strain mouse pups produced fewer sounds in contact with bedding of adult CBA mice than when exposed to genetically unrelated cues of C57BL and DBA adult animals. The pulses were also significantly shorter in the presence of odour of CBA mice than when exposed to another strain. Newborns emitted the shortest signals when in contact with urine of CBA virgin females, but there were no differences in vocalizations in response to odours from intact, castrated, and testosterone-treated castrated CBA males. These results confirm that CBA pups can distinguish the odour of their genotype. The paper also presents the first evidence that CBA pups discriminate the sex of adult animals and that the chemosignals recognized by pups are secreted with urine but are not testosterone-dependent.