The present study evaluates the extent of axillary dissection as part of the primary surgical treatment of operable breast cancer. Data are from the period January 1979 to August 1990 and were collected prospectively as part of the Danish Breast Cancer Cooperative Group protocols for low-risk mammary carcinoma. The series consists of 6774 breast cancer patients aged 69 years or younger. The number of axillary lymph nodes removed was related to the frequency of ipsilateral axillary recurrence, recurrence-free survival, and overall survival after a median of five years follow-up, respectively. The recurrence-free survival and overall survival rate were directly related to the number of axillary lymph nodes removed. The difference in outcome is believed to be caused by false-negative classification of axillary-positive high-risk patients in groups of patients where only a few axillary lymph nodes were removed.