SummaryInferior vena cava thrombosis is a well-recognized complication of filter insertion. We report on two patients who presented with progressive exertion dyspnoea and lipothymia revealing a complete inferior vena cava thrombosis below the filter. Haemodynamic exploration demonstrated that cardiac output could not adapt during upright exercise owing to inappropriate cardiac preload. Since these general manifestations can precede any symptom of lower limb venous stasis, thrombosis of inferior vena cava has to be carefully searched in this setting. The pathogenesis of this unusual complication is reviewed in the light of experimental models of vena cava ligation.