Innovative treatment programs can be implemented successfully in hospitals only if key actors take on leadership responsibility for the new programs. Implementation of an innovative Addictions Day Treatment Program (ADT) for alcohol and substance abusers in a 156-bed community hospital is reported. Implementation issues for staff psychiatrists, psychologists, psychiatric nurses, and hospital administrators are the primary subject of this article. Participation of these professional groups depended on their treatment ideology, the threat they perceived the program to be to patients, the time demanded of them, whether they would be reimbursed for providing care by the program, and the changes the program introduced in provider-patient interaction. The way shared responsibility among key hospital and unit leaders made it possible to overcome resistance to the program and to develop a positive consensus about day treatment is shown.