OBJECTIVE: Major depressive disorder (MDD) is projected to rank second on a list of 15 major diseases in terms of burden and is highly recurrent in nature. Accordingly, efforts to reduce the disabling effects of this chronic condition should shift to preventing recurrence after response to a acute treatment. INTERVENTION: The best established effective psychological intervention is cognitive therapy, with indications for prophylactic effects after remission. In this study (cost-) effectiveness of Continuation preventive cognitive therapy (C-C-PCT) after response to acute CT (A-CT) will be examined in comparison with care as us usual (CAU). DESIGN: A randomized controlled clinical trial in two parallel groups comparing (1) C-PCT after A-CT versus (2) CAU after A-CT, with follow-ups at 3, 6, 12 and 15 months. Randomisation will be stratified for number of previous episodes and the level of residual symptoms. STUDY POPULATION: Patients that responded to A-CT treatment with at least two previous depressive episodes. OUTCOME MEASURES: Primary outcome; cumulative person-time based incidence of depression relapse/recurrence over 15 months using DSM-IV-TR criteria as assessed by the Structural Clinical Interview for Depression. Secondary outcome severity: symptom severity as measured with the Inventory of Depressive Symptomatology (IDS-R).