We describe a 56-year-old woman suspected of Fanconi anemia on the basis of the following clinical findings: microcephaly, short stature, congenital deafness, and the clinical findings in her deceased brother. Hematologic or other signs of malignancy were absent. The diagnosis was confirmed by demonstrating hypersensitivity of her lymphocytes to mitomycin C (MMC). Cell fusion experiments indicated that the patient belongs to complementation group A. The patient's brother died at the age of 50 of heart and renal failure, and anemia. He had clinical findings similar to those of his sister, and a horseshoe kidney. From 31 years on he had thrombocytopenia and leucopenia. Both patients had insulin-dependent diabetes mellitus. A chromosomal breakage test carried out elsewhere before his death failed to demonstrate MMC hypersensitivity of his lymphocytes, which led to the investigation of his sister. To our knowledge these two cases are the oldest Fanconi anemia patients reported thus far.