Abstract. Winnewisser J, Rossi M, Spa$ th P, Bu$ rgi H (Bu$ rgerspital Solothurn and Bluttransfusionsdienst, Bern, Switzerland). Type I hereditary angio-oedema. Variability of clinical presentation and course within two large kindreds. J Intern Med 1997 ; 241 : 39-46. Objectives.Hereditary angiooedema (C1-inhibitor deficiency) is a disease with protean manifestations which is often misdiagnosed initially. The purpose of this study was to delineate the clinical spectrum and course of this potentially life-threatening disease. Setting. Ten members of two unrelated affected kindreds were repeatedly hospitalized in our service with attacks of angiooedema. Among the 271 members of the two kindreds 69 were identified who reported typical attacks. Design and subjects. Detailed information on the clinical course and laboratory data (C1-inhibitor concentration and activity, C4 concentration) were obtained from 59 of the 69 affected subjects. Results. C1-inhibitor concentration and activity were low in all affected patients. The disease had become manifest by age 30 years in 98 %. Most patients suffered from attacks of subcutaneous swellings and abdominal pain, and half of the patients have had