Both animal and human studies imply that aggressive behaviour is associated with increased dopaminergic transmission. Our hypothesis was that impulsive violent offenders have also higher heterogeneity of the striatal dopamine transporter (DAT) density than controls. We performed a fractal analysis in 21 impulsive violent offenders, 10 non-violent alcoholics and 21 controls to measure the heterogeneity and laterality of the striatal DAT density characterised by [123I]beta-CIT single-photon emission tomography (SPET). The [123I]beta-CIT distribution was significantly more heterogeneous in the right striatum of violent offenders than in healthy controls. In addition, in young violent offenders there was no normal left-to-right asymmetry observed in control subjects of the same age. The normalisation of the left-to-right asymmetry may reflect late neurobiological maturation.