The extra coagulation effects of prekallikrein and of the other factors of the contact phase of blood clotting have received great attention in the past few years.The clinical observation that hypertension was present in two families with congenital prekallikrein deficiency prompted a survey of all reported cases of this disorder.Altogether, 89 cases of proven prekallikrein deficiency have been described in the literature. Hypertension or vascular complications of it were found in 21 patients (12 men and nine women). If the analysis is limited to patients over 25 years of age, the number becomes 21 out of 64 cases (38.2%).This prevalence is much higher than that seen for other conditions occasionally found in patients with prekallikrein deficiency, namely hyperthyroidism, lupus erythematosus, chronic lymphocytic leukemia, kidney malformation, peptic ulcer, and myelofibrosis (1-2%).These results indicate the need to investigate further the relation between prekallikrein deficiency and hypertension.