A case of severe angioedema with several episodes of life-threatening attacks faring a follow-up of 7 years is presented. Although the biologic profile is that of an acquired C1 ̄ INH deficiency, no lymphoproliferative malignancy or immune-complex disease could be proven until now. However, the patient has had a small monoclonal IgG λ-gammopathy for 4 years. During the last 4 years, edematous manifestations have stopped. The patient now suffers at regular intervals of about a week from short-lasting attacks with digestive and vasomotor symptoms. This clinical evolution is accompanied by a worsening in the complement abnormalities. The digestive and vasomotor attacks were found to be correlated with sudden prekallikrein and high-molecular-weight kininogen consumption. These findings demonstrate that prekallikrein is activated during acquired C1 ̄ INH deficiency and that the products of this pathway such as bradykinin are probably responsible for a part of the clinical manifestations associated with this disorder.