Cytogenetic studies were performed on six patients with multiple myeloma in which G-banding allowed the identification of clonal chromosome abnormalities. Normal cells and random chromosome gains and losses were seen in all cases. Numerical clonal aberrations were observed in two cases. Among the remaining cases, clonal chromosome rearrangements were seen in two cases, whereas, the other two patients revealed both numerical and structural clonal anomalies. The following marker chromosomes were identified: 1q-, 2p+, 2q+, 7q-, 17p-, and five unidentified abnormal chromosomes.