In a retrospective study of primary lymphedema, we found that the age of onset ranged from 0 to 16 years; sex did not appear to be a factor; and treatment was preventive rather than surgical. Thirteen patients were available for follow-up studies, the time interval being at least 6 years. The degree of swelling at the time of the follow-up examination was defined as mild, moderate, or severe. In patients with mild and moderate swelling the edema was not progressive and surgical treatment was not indicated. Severe swelling appeared to be associated with congenital lymphedema and with repeated infection. Pressure-support treatment can be effective in the reduction of swelling or in the prevention of further swelling, if applied constantly over a long period of time. The authors discuss the histological similarity between lymphedema and lymphagioma, and present an anatomical classification for the two entities.