A 40-year-old woman was referred to our hospital with severe hypovolemic shock and anasarca. The laboratory findings showed marked hemoconcentration and a decrease in total serum protein with the presence of monoclonal IgG-lambda. She had had a similar episode of generalized edema 2 years previously. We diagnosed the patient as having typical systemic capillary leak syndrome (SCLS) and she improved gradually after infusion of albumin-containing fluid. SCLS is a very rare condition caused by unexplained episodic capillary hyperpermeability. Its treatment has remained largely supportive and the prognosis is generally poor. Awareness of SCLS is necessary for improvement of the outcome.