PURPOSE: Modified radical mastectomy is the most commonly performed operative treatment because of extensive microcalcifications, multicentric tumors, early pregnancy, and patient preference, despite of the eligibility of many women for breast-conserving surgery. Various modifications of this operation have been described, including preservation of the pectoralis minor, resection of the pectoralis minor, and division of the origin of the pectoralis minor. The purpose of this study was to identify the indications of Scanlon's technique by evaluating the benefit of complete axillary dissection and the cosmetic results of chest walls in patients who had undergone a modified radical mastectomy (MRM) for breast cancer. METHODS: In fifty nine patients who had undergone MRM for infiltrating breast cancer from January 1992 to December 1997 and performed follow-up study of CT of chest walls, we examined operative techniques, dissected & involved axillary lymph nodes (ALNs) retrospectively and atrophy of pectoralis muscles by clinical examination and CT findings of chest walls. RESULTS: We analyzed all the results of aforementioned study, based on various operative techniques. The largest groups were Auchincloss of 63.6% in stage IIA, Scanlon of 50% in stage IIB and Patey of 28.6% in stage IIIA. The mean numbers of harvested ALNs were 20.4 in Scanlon, 20 in Patey and 15 in Auchincloss. The largest groups were Auchincloss of 77.3% in the harvested ALNs of 10-19, Scanlon of 40% in the harvested ALNs of 20-29 and Patey of 14.3% in the harvested ALNs of 30-39. The mean numbers of involved ALNs were 4.4 in Patey, 2.6 in Scanlon and 0.9 in Auchincloss. The largest groups were Auchincloss of 63.6% in the non-involved ALNs, Auchincloss of 31.8% in the involved ALNs of 1-3, Scanlon of 20% in the involved ALNs of 4-9 and Patey of 28.6% in the involved ALNs of 10 or more. Through the clinical examinations and CT studies of chest wall, such changes of chest walls were found, as suggestive of injury of medial pectoral nerve of 2 cases (9.1%) and of lateral pectoral nerve of 1 case (4.5%) inAuchincloss, of injury of medial pectoral nerve of 1 case (3.3%) in Scanlon and of injuries of medial pectoral nerve of 3 cases (42.9%) and of lateral pectoral nerve of 1 case (14.3%) in Patey. Postoperative complications were arm lymphedema of 1 case in each technique and anemia of 4 cases (13.3%) in Scanlon. CONCLUSION: We conclude that in the MRM for patients with resectable breast cancer, Scanlon's technique is superior to Auchincloss or Patey in preventing axillary recurrence and atrophies of pectoralis muscles by successful complete axillary dissection with preservation of medial and lateral pectoral nerve in cases of more advanced stage over stage IIB with involved ALNs of one to nine. However Patey's technique seems to be necessary in cases of metastasis of the interpectoral node or the subclavicular node regardless of poor results of cosmesis.