Lymphedema results from impaired lymphatic transport with increased limb volume. Primary and secondary forms can be distinguished. Secondary lymphedema of the upper limb is the most frequent in France. A 2-cm difference on any segment of the limb confirms the diagnosis of lymphedema. Calculated lymphedema volume using the formula for a truncated cone is required to assess the efficacy of treatment and to monitor follow-up. Primary lymphedema is sporadic but rarely familial. Lymphoscintigraphy is useful in the primary form to evaluate precisely lymphatic function of the two limbs. Erysipelas is the main complication,but psychological or functional discomfort may occur throughout the course of lymphedema. Lipedema is the main differential diagnosis, defined as an abnormal accumulation of fat from hip to ankle and occurs almost exclusively in obese women.