In a group of eighteen dogs (1977-79) artificially interrupted lymphatics have been bridged by suitable small vein grafts. Patency was controlled by different methods: by clinical microscopical control, by microlymphangiography and by histological examinations. The patency rate in this group was 61.1 per cent. So for the first time it could be shown experimentally that it is possible to restore interrupted lymphatics by grafting. This might be the basis for a causal therapy of secondary lymphedema by reconstruction of interrupted or occluded lymphatics. In a further group of fifteen dogs different autologous grafts have been compared. Each five lymphatic, venous and arterial grafts have been interposed in lymph collectors of 0.3 to 0.6 mm in diameter by the same surgeon applying the same microsurgical and atraumatic technique. The grafts varied from 8 to 25 mm in length. While all the lymphatic grafts remained patent, one of the five venous and all arterial grafts were occluded. There could not be found any correlation of patency rate to length of the grafts. Light microscopical and electron microscopical examinations of the harvested vessels showed heavy pathological findings of the arterial walls. In the venous grafts the intima was thickened to different extent. This could be explained by the lack of blood supply from the lumen. Very likely the occlusion of all arterial grafts seems to be explained by the disturbance of the vessel wall blood supply. The lymphatic grafts histologically showed nearly no pathological damage. There was complete reendothelialization at the suture line of all patent grafts. From these experimental results it is concluded that arteries are not suitable for interposition in order to restore lymph drainage. It could be shown that veins and lymphatics are equally usable for this purpose. Therefore these two structures have been used clinically in cases of therapy resisting lymphedemas for reconstruction of the destroyed lymph paths.