Although relatively uncommon, numerous cases of maternal neonaticide have been reported. To date, only two cases of paternal neonaticide have appeared in the literature. The authors review neonaticide and present two new case reports of paternal neonaticide. A psychodynamic explanation of paternal neonaticide is formulated. A new definition for neonaticide, more consistent with biological and psychological determinants, is suggested. 27 references. (Author abstract)