Information on infant killing by males is reviewed and extended by personal communications and observations. Most cases of infant killing reported occurred during periods when a new alpha male was establishing himself and during arranged encounters of strangers or unfamiliar individuals in captivity. There seem to be no specific releasing stimuli for infant killing, but rather the lack of familiarity between male and females, their nonacceptance of him in the whole set of roles tied to the alpha status, and his special motivational condition as new alpha lead him to a state, in which attacks on infants may result. Infant killing is considered to have a selection advantage by increasing one’s own reproduction success while reducing the one of other males.