The great majority of adult Swiss albino males exhibit infanticide when sexually naive, but after mating and cohabitation with females they show paternal or amicable behaviour towards pups. A preliminary experiment was designed to see whether kin recognition mechanisms might also be involved in the inhibition of infanticide. To this purpose, previously selected infaticidal males which underwent a sequential experience of territory acquisition, mating and cohabitation with females during pregnancy but were separated from the female before parturition (18–19 days) were confronted with their own or unrelated infants in the presence or absence of familiar females and inside or outside their marked area (territory). In all cases infanticide never occurred. These data cast strong doubts on a direct (i.e. genetic or «mother labelling») kin discrimination of young by males. It is important to note that even the location where the male met pups did not change the behaviour towards related or unrelated infants. The social organization of this species consists of a reproductive territory in which the majority of litters are sired by the territorial holder dominant male. It seems that selection has operated to inhibit infant killing, through sexual interaction with females, at times when there is a strong probability that a male will face its own preweanling pups. In terms of ultimate causes this behaviour results in kin selection (i.e. favouring the survival of related infants) without necessarily involve kin discrimination processes. On the basis of present findings a general criticism of the use of the indirect kin recognition term is discussed.