Method. In an uncontrolled study with 24 formerly depressed patients, rumination was assessed with the Ruminative Response Scale. To assess the occurrence of relapse or recurrence, the Structured Clinical Interview for DSM-IV was administered 12 months after the end of the MBCT. Results. Rumination significantly decreased during the MBCT course. Post-treatment levels of rumination predicted the risk of relapse of major depressive disorder in the 12-month follow-up period even after controlling for numbers of previous episodes and residual depressive symptoms. Conclusions. The results provide preliminary evidence that rumination is important in the process of depressive relapse.