The investigation of compliance in patients with major depressive disorder (in drop-outs versus completers and in first episode versus recurrent episode patients). A total of 85 outpatients with major depressive disorder were followed for 6 months. Different dimensions of compliance were investigated: drop-outs versus completers and their medication adherence (with electronic monitoring). General linear mixed models were applied to examine the time courses of adherence. Drop-out rates were higher in younger patients and in patients with a lower initial depression severity. The adherence during 6 months of treatment with selective serotonin reuptake inhibitors was above 80 in 70% of the patients. The adherence decreased by 2.5% per month and decreased more than three times more rapidly in drop-outs (from baseline to time of drop-out). A medical visit resulted in a temporary increase in pill intake. General linear mixed model analysis showed that the predicted outcome was worse in drop-outs than in completers and worse in recurrent episode patients than in first episode patients (the former showing a higher adherence). Adherence decreases with time during 6 months of treatment with antidepressants and is influenced by demographic and clinical variables. Completers show a higher adherence than drop-outs. The outcome was worse in recurrent episode patients than first episode patients although they had a higher adherence.