Possible drainage pathways for the [human] upper extremity after axillary lymphadenectomy was studied by means of Indian ink injection. The single drainage is through the lateral upper arm bundle, but only if the latter joins the supraclavicular nodes or if its infraclavicular ending remains unremoved. The lateral bundle occurs as a long or short type. With regard to the lymphatic drainage of the skin or areolae, zones and territories can be distinguished. A long bundle is the more suitable collateral way as collectors of the forearm territory join it. The most frequent cause of lymphedema is the fact that lymph of the forearm and of the dorsomedial upper arm territory can reach the lateral bundle only via the cutaneous plexus over the lymphatic watersheds.