Cytogenetic studies were performed on a malignant fibrous histiocytoma of bone and its metastasis to lung. Numerical chromosome abnormalities were described for all chromosomes except chromosomes 2, 4 and 16. Structural abnormalities in the primary tumor involved chromosomes 1, 3, 5, 10, 11, 13, 15, 16 and 17. The chromosomal rearrangements seen both in the primary tumor and its metastasis involved chromosomes 13, 15 and 17. Two X chromosomes contained large homogeneously staining regions (HSRs) in the primary tumor which were replaced by multiple double minutes (DMs) in the metastatic tumor.