We have studied eight patients, six children and two adults, during a microepidemic of soil- and patient-proven histoplasmosis. Pulmonary function tests were performed between the 15th and 23rd days after the onset of symptoms, and repeated between the fifth and sixth, the ninth and tenth and the 15th and 22nd months afterward. Initial abnormalities were mild in seven cases and severe in one. There was a restrictive pattern in three cases and an obstructive pattern in two. The fraction of CO extraction was reduced in five cases and the diffusing capacity for CO was reduced in five of six cases so tested. Hypoxemia was present in three cases. On follow-up, the obstructive defect had disappeared by the sixth month, the restrictive pattern by the tenth month, and the diffusing defect still remained in three cases by the end of follow-up. Hypoxemia remained only in the severe case.