Behaviour management problems (BMP) are common among children (4-12%) and the prevalence seems to be rising. Persistent antisocial behaviour often leads to poor long-term psychosocial adjustment. Structured parent-training programmes have proven to be the most effective way of treating BMP in young children. The Incredible Years Series (IYS), which is a manual-based programme, was introduced in Sweden in 2001. Its aim was to evaluate the effectiveness of IYS in diverse clinical settings in Sweden. Parents of 113 children (3-9 years), recruited through the IYS-trained group leaders? ordinary services, participated in the study. The parents answered various questionnaires regarding their children?s symptoms and their own psychological well-being before and after participating in the parent-training groups. The results are very encouraging; significant reduction of BMP in the children was found on all relevant measures. A significant increase in the self-rated well-being of the mothers was also found. The IYS seems to work in Sweden, even when used by group leaders who are in training. The importance of using a well-documented manualized method when implementing new models is accentuated.