The transfer of successful interventions between different contexts is of increasing interest to policy makers, practitioners and researchers. This study considers the findings of a Swedish trial of multisystemic therapy (MST) in relation to the findings of other such trials in the US and Norway. The trial assessed treatment outcomes two years after referral to MST or treatment as usual (TAU) for 156 young people meeting the diagnostic criteria for conduct disorder. A mixed factorial design was used. With an intent-to-treat approach, the results showed a general decrease in psychiatric problems and antisocial behaviours among participants across treatments. There were no significant differences between the two groups, and the lack of treatment effect did not appear to be caused by site differences or variations in programme maturity.