Axillary lymph node dissection for staging the axilla in breast carcinoma patients is associated with considerable morbidity, such as edema of the arm, pain, sensory disturbances, impairment of arm mobility, and shoulder stiffness. Sentinel lymph node biopsy electively removes the first lymph node, which gets the drainage from the tumor and should therefore be associated with nearly zero morbidity. Postoperative morbidity (increase in arm circumference, subjective lymphedema, pain, numbness, effect on arm strength and mobility, and stiffness) of the operated arm was prospectively compared in 35 breast carcinoma patients after axillary lymph node dissection (ALND) of Level I and II and 35 patients following sentinel lymph node (SN) biopsy. Patient characteristics were comparable between the two groups. Postoperative follow-up was 15.4 months (range, 4-28 months) in the SN group and 17.0 months (range, 4-28 months) in the ALND group. Following axillary dissection, patients showed a significant increase in upper and forearm circumference of the operated arm compared with the SN patients, as well as a significantly higher rate of subjective lymphedema, pain, numbness, and motion restriction. No difference between the two groups was found regarding arm stiffness or arm strength, nor did the type of surgery affect daily living. SN biopsy is associated with negligible morbidity compared with complete axillary lymph node dissection. Copyright 2000 American Cancer Society.