A newly recognized patient with the factor X Friuli coagulation disorder is presented. The propositus is a 10-year-old boy who presented excessive bleeding after a tooth extraction. This is the 11th patient with this peculiar coagulation disorder discovered in Friuli and the 12th so far described. His parents are consanguineous and heterozygotes together with other family members. The main laboratory features, typical of the disease, were a prolonged prothrombin time, a prolonged partial thromboplastin time, and a normal Stypven-cephalin clotting time. The incidence of the homozygotes in the Friuli area appear to be 0.000005 (11 cases in a population of 2,000,000). The probable frequency of the abnormal f gene is 0.0033, whereas that of the normal gene F is 0.9967. The theoretical frequency of the heterozygote, Ff condition is 0.007, namely 7 heterozygotes every 1,000 persons. However, only about 70 ascertained heterozygotes have been discovered so far.