The systemic capillary leak syndrome (Clarkson's syndrome) is a rare idiopathic disorder, characterized by recurrent episodes of hypovolaemic shock, haemoconcentration and hypoalbuminaemia due to a sudden shift of fluid and macromolecules from the intravascular to the interstitial space. A young man is presented in whom recurrent attacks of hypotension and diffuse swelling were initially attributed to staphylococcal toxic shock syndrome. With the additional finding of a monoclonal gammopathy, the diagnosis of systemic capillary leak syndrome was made. Recognition of this syndrome is important, as prophylactic treatment with terbutaline and theophylline may be beneficial in this life threatening syndrome.