In November 1994, private physicians and public health officials in Cleveland, Ohio, and CDC reported a cluster of eight cases of acute pulmonary hemorrhage/hemosiderosis that had occurred during January 1993-November 1994 among infants in one area of the city. Two additional cases were identified in December 1994. All 10 infants lived within seven contiguous postal tracts in eastern metropolitan Cleveland. Pulmonary hemorrhages recurred in five of the infants after they returned to their homes shortly after hospital discharge; one infant died as a result of pulmonary hemorrhage. This report summarizes the findings of the follow-up investigation, including a case-control study and an assessment by the county coroner of cases of infant death. These findings documented an association between acute pulmonary hemorrhage/hemosiderosis in this cluster of cases and mold growth in their water-damaged homes.