METHODS: We used a randomized encouragement design to study the effects of assisting 6 managed care organizations to implement collaborative care for depression in 30 experimental and 16 control practices. We identified a total of 920 depressed patients and referred them to their clinical practice site' s collaborative care program. Access to the program was through a nurse care manager. Care managers recorded all patient contacts on pre-structured forms. Patients completed self-administered surveys at baseline and every six months. Our evaluation uses bi-variable and multi-variable regression analyses. RESULTS: Overall, 73%of patients completed initial assessment visits. There was considerable variation among sites in adherence to the care management protocols, e.g., assessment of patient treatment preferences at the initial visit ranged from 18%to 100%at different sites (73%of patients assessed overall).