Ninety females underwent mastectomy for breast cancer and were thereafter investigated to determine whether nerve entrapments were responsible for some of the disabling symptoms in their arms. The majority of these patients suffered from fullness (edema), numbness, paraesthesia, weakness and pain of the arm on the mastecotmized side. Lymphedema of varying degrees found in 50% of these patients was associated with brachial plexus entrapment and carpal tunnel syndrome (CTS). 28% of the patients has CTS, and 28% suffered from brachial plexus entrapment of the arm on the mastecotmized side, as compared with 8% and 5%, respectively, on the nonoperated side. 12% of the patients suffered from both types of entrapment. Thus we consider that brachial plexus entrapment and carpal tunnel syndrome should be added to the list of complications following mastectomy, with lymphedema playing an active part in their development.