Most research on anger and aggressive behaviour management has focused on male offenders. Little is known not only about the types and seriousness of violent female behaviour, but also about the treatment needs of violent female offenders. This article describes a qualitative study on violent females, examining their aggressive behaviour and describing experiences with Emotion Control Therapy (ECT), an adaptation of the Dutch version of Goldstein's Aggression Replacement Training. Firstly, specific issues in treatment needs for developing the programme are examined. After describing the design and content, special attention is given to practical experiences with this ambulant therapy. Then some qualitative results from three ECT groups are presented, in which differences in certain personality and behavioural characteristics between violent females and violent males are described. Recommendations are made for adapting ECT to the specific needs of this population, based on these results.