As part of the development of a quality of life monitor for women with breast cancer, a qualitative acceptability test was conducted among 10 patients, to assess their suggestions for improvement. Next, a field test was conducted among 50 women with breast cancer receiving radiotherapy, chemotherapy, or both treatments to examine the use of the monitor in daily practice and to assess physicians' and patients' experiences with the monitor. Although patients in general held a positive attitude toward the monitor and compliance was high, patients regularly were unsure about how the quality of life information was used by physicians.