The paper presents the findings of an experimental study of childhood aggression. It contains a description of manifestations of childhood aggression and psychological characteristics of preschool children predisposed to aggressive behaviour. A comparative study of aggressive and non-aggressive children aged 5 and 6 has revealed peculiarities of intellectual, volitional and communicative development of an aggressive child. Analysis has also revealed individual variations of childhood aggression as well as those peculiarities of aggressive children that manifest themselves in relation to peers.