The aim of the study was to evaluate the clinical and prognostic significance of cytogenetic abnormalities in multiple myeloma patients. Cytogenetic studies were performed in 95 myeloma patients aged 31-82 (median 64) prior to chemotherapy. The GTG and CBG chromosome banding were performed and chromosomal abnormalities were described according to International System for Human Cytogenetic Nomenclature ISCN (1995). An abnormal karyotype was observed in 29% myeloma patients. Patients with an abnormal karyotypes showed various numerical and structural aberrations with hyperdiploidy in 39%, hypodiploidy in 39% and pseudodiploidy in 18% of patients. Monosomy of chromosome 13 was present in 29% of patients with an abnormal karyotype. Multiple myeloma patients with chromosomal abnormalities had more advanced disease than those with normal karyotype (82% vs 57% had stage III myeloma). beta 2-microglobulin and LDH levels were higher and hemoglobin level was significantly lower in patients with an abnormal karyotype. The plasma cell involvement of bone marrow was significantly higher in these patients. Overall survival was significantly shorter of patients with abnormal karyotypes (median 24 months vs 18 months), particularly of patients with monosomy of chromosome 13 (median 14 months). Cytogenetic studies are helpful to evaluate the prognosis and treatment options in multiple myeloma patients.