The occurrence of thrombotic events in patients with congenital bleeding conditions has received considerable attention in recent years. The same is true for asymptomatic defects of factors of the contact phase of blood coagulation, mainly FXII. Anecdotal reports on thrombosis in patients with prekallikrein deficiency have occasionally been reported. These involved both arterial and venous thrombosis. The purpose of the present article is to analyze the stories and the clinical pictures of all 75 cases of prekallikrein deficiency published so far. Among these patients were 9 with thrombosis, 6 arterial (myocardial infarction and ischemic stroke) and 3 venous (deep vein thrombosis with or without pulmonary embolism). In 6 cases acquired thrombosis risk factors were present; in 2 cases no associated risk factors were present and in 1 case no information was supplied in this regard. One patient who presented both a stroke and a pulmonary embolism had a fatal outcome. The article clearly indicates that prekallikrein deficiency does not protect from thrombosis in spite of the severe in vitro coagulation defect.