(1) Clinical observations of 33 cases of aortitis syndrome were described. They consisted of 22 cases of pulseless disease and 11 of atypical coarctation of the aorta with or without renal arterial narrowing. Autopsy examination was made on 2 of them. An intimate relation between pulseless disease and atypical coarctation was emphasized on the basis of the similarity in geographic incidence, sex and age distribution, some laboratory data, aortographic pictures and pathological findings. (2) Anti-aorta antibody was detected from the serum in 12 of 14 cases of aortitis syndrome by complement fixation test, suggesting the participation of autoimmune mechanism in the development of aortitis syndrome.