Depression is a recurrent disorder. Given the high risk of relapse it is important to study how patients relapse in depression. This thesis, which focused on recurrent depression specifically, showed that it is not so much mood activated dysfunctional thinking patterns that predict relapse in depression, but rather mood itself. Moreover, Preventive Cognitive Therapy, an effective treatment to prevent relapse in depression, did not appear to work through reduction of activation of mood-linked thinking patterns. However, we have to keep the restrictions of our statistical analysis in mind. Currently we still do not know how preventive interventions exert their effects. Having remitted patients rate their own mood by marking a cross on a 10-centimeter line was able to predict relapse in depression over 5.5 years, with patients scoring higher being more vulnerable for relapse. This ‘emotion meter’ was also able to predict current depression status quite accurately, although it somewhat overestimated the number of patients truly having a current depression (false positives). It appeared to be the case that remitted patients who had a higher number of previous depressive episodes had higher levels of sad mood after remission. Possible, an ‘emotional scar’ is formed in terms of sad mood that remains after exposure to more previous depressive episodes. With our design we can however not exclude an alternative explanation, being that high levels of sadness prior to first-episode onset exposed these patients to higher risk of developing recurrent depression to begin with. This should be examined more closely. Finally, daily hassles also predicted depressive symptomatology later in time. Having a comorbid personality disorder was also related to characteristics that we know make patients vulnerable to relapse in depression