A linkage between prorenin, renin, and intrinsic coagulation systems has been suggested recently. We studied the behavior of renin, prorenin, and kallikrein in a patient affected by congenital factor XII deficiency. Captopril test, upright posture, and furosemide administration provoked in our patients changes of renin and prorenin similar to those found in normal and hypertensive subjects. Unchanged kallikrein levels confirmed that no interaction between prorenin activation and factor XII-kallikrein system appears to be present.