This paper investigates how a mandatory activation program in Denmark affects the job finding rate of unemployed workers. The activation program was introduced in an experimental setting where about half of the workers who became unemployed in the period from November 2005 to March 2006 were randomly assigned to the program while the other half was not. It appears that the activation program is very effective. The median unemployment duration of the control group is 14 weeks, while it is 11.5 weeks for the treatment group. The analysis shows that the job finding rate in the treatment group is 30% higher than in the control group. This result is mainly driven by the more intensive contacts between the unemployed and the public employment service.