Late treatment-related morbidity after mastectomy and adjuvant systemic treatment with and without postoperative irradiation was assessed in 84 patients randomized in the Danish Breast Cancer Cooperative Group Trials 82b and c. A structured interview and physical examination, using a standardized assessment sheet, constructed on the basis of the late effects normal tissues (LENT) scoring system, was used. The median length of follow-up from mastectomy was 9 years (range 6-13 years). Lymphedema was measured in 14%, of the irradiated patients versus 3% of the non-irradiated patients (NS). Slightly decreased shoulder morbidity was measured in 45% of the irradiated women versus 15% of the non-irradiated patients, but moderate or more severe impairment was seen in only 5% of the irradiated patients and in none of the non-irradiated patients (p = 0.004). Seventeen percent of the irradiated patients and 2% of the non-irradiated patients found that impairment of shoulder movement caused symptoms (p = 0.001).