In the Netherlands, the Depression Initiative has been launched in 2006 as a nationwide attempt to implement the Multidisciplinary Guideline for Depression and to evaluate its cost effectiveness. An evaluation of the selected strategy to implement the guidelines, a Breakthrough Collaborative, was conducted as a quasi experimental trial. The intervention group consisted of around 530 patients coming from 10 multidisciplinary teams in primary care. The intervention teams received a set of implementation strategies, as part of the Breakthrough Method, developed by the Institute for Healthcare Improvement (www.ihi.org). The aim of the participants in this implementation project was to implement guideline recommendations directed at a reduction of unnecessary antidepressant treatment for patients with mild depression, better use of effective, but minimally invasive treatment options and improved antidepressant and psychotherapeutic treatment for patients with severe symptoms. Monitoring depression severeness was also one of the goals. This guideline derived, stepped care approach was compared to Care As Usual in the primary care setting, as provided in a different study group (NESDA). Outcomes were measured in terms of quality of care provided by the general practitioner (antidepressant prescription rates) and clinical outcomes (BDI, IDS-SR, WHODAS). A process evaluation and simple economic evaluation was part of the study design. In the presentation, preliminary results will be presented.