Four patients with hereditary lymphedema present at birth (Milroy's disease) have been studied by fluorescence microlymphography (1, 7). The videomicroscopy technique failed to visualize any lymphatic capillary in the edematous part of their legs. In sporadic primary lymphedema with late manifestation, however, a well developed superficial capillary network is detected (1, 6). Three family members without lymphedema had normal microlymphatics. Milroy's disease, at least in the family presented, is characterized by aplasia or extreme hypoplasia of both lymphatic capillaries and collectors whereas in the usual sporadic form of primary lymphedema aplasia or hypoplasia is confined to the larger trunks.