Breast cancer patients experience significant physical, psychological stress in the time after diagnosis and treatment completion. Fear of recurrence, anxiety, depression and reduced quality of life are common. The Mindfulness-Based Stress Reduction (MBSR) programme was developed by Jon Kabat- Zinn in 1979 and has been found effective in relieving emotional stress and other psychological and psychosomatic symptoms in a variety of patient groups, including cancer patients. Seven studies have quantitatively assessed the effect of the MBSR programme on stress in breast cancer patients. They applied stress questionnaires and measured cortisol in the subjects. Six of the studies found a significant reduction of stress levels in the participating women. There was one randomised controlled study, and this study did not find a significant effect of the MBSR intervention. Main validity issues were lack of randomisation and control groups, small sample sizes and lack of long-term follow-up. It can be concluded that the MBSR programme is feasible to deliver in a clinical setting to breast cancer patients, and that there is interest and motivation in the patient group for MSBR. Although there is evidence that MBSR has a positive effect on stress in mixed cancer patients, there is a need for larger, randomised controlled studies to be able to definitely conclude that MBSR has the same effect in breast cancer patients.