This study was undertaken to clarify the characteristics of pneumatization with aging by measuring the area of temporal pneumatizations of malformed ears as shown in roentgenograms. Roentgenograms of 23 patients afflicted unilaterally and 8 bilaterally with congenital atresia auris with microtia were examined. These patients, aged 3 to 27 years, were admitted to the Department of Otolaryngology, Okayama University Medical School Hospital for surgical treatment from January 1953 to Novembar 1978. A considerable number of X-ray photographs of normal ears of outpatients of the same hospital were used for statistical comparison during the same period. It was revealed that the area of pneumatization was statistically smaller in the malformed ear, and that the correlation between the area of pneumatization and age was high in the nomal ear. There was some difference between the bitateral and unilateral cases as to the mode of the development. In bilateral cases, it was thought that the development of pneumatization might have occurred during the embryonal stage and be attributable to congenital causes. Pneumatization in unilateral cases might have been influenced strongly by postnatal suppression.