The protein-loosing enteropathy (PLE) may result from a broad variety of underlying diseases. These conditions are of systemic nature or locally affecting the gastrointestinal tract. Major symptoms are oedema due to low plasma protein levels. Gastrointestinal symptoms are not necessarily present. The diagnosis is confirmed by the finding of increased faecal concentrations of Alpha-1-Antitrypsin (> 320 mg/L). In the majority of cases, in which underlying diseases are present, the etiology is obvious. In unclear cases the differentiation into inflammatory or circulatory disturbances or alterations of the architecture of the basal membrane is helpful. An economic, staged approach is presented. To localize the site of protein loss imaging is required (abdominal ultrasound, CT-scan, endoscopy and Technetium-Scan). If a circumscribed intestinal source of protein loss is suspected which may be amenable to surgery, intraoperative enteroscopy should be considered. If causal treatment is impossible; intravenous replacement of albumin and immunoglobulines in intervals from 1 to 4 weeks will be necessary. The prognosis in patients with isolated PLE is good. Otherwise it depends on the underlying disease.