Summary Two cases of pulmonary calcification occurring in twins have been presented, the first patient having had symptoms since January, 1947, and the second being asymptomatic. In neither case has the etiological agent been identified. The tuberculin and coccidioidin skin tests in both children were negative, whereas the histoplasmin skin tests were positive. These cases may represent subclinical forms of histoplasmosis. When and in what locality the pulmonary calcifications first appeared is not known since the children have lived in many different states.