Background Much is known about the cytogenetic lesions that characterize multiple myeloma (MM) patients from the USA,Europe,and East Asia.However,little has been published about the disease among Southeast Asians.The aim of this study was to determine the chromosomal abnormalities of MM patients in our Singapore population.Methods Forty-five newly-diagnosed,morphologically confirmed patients comprising 18 males and 27 females,aged 46-84 years (median 65 years) were investigated by karyotyping and fluorescence in situ hybridization (FISH).FISH employing standard panel probes and 1p36/1q21 and 6q21/15q22 probes was performed on diagnostic bone marrow samples.Results Thirty-four cases (75.6％) had karyotypic abnormalities.Including FISH,a total detection rate of 91.1％ was attained.Numerical and complex structural aberrations were common to both hyperdiploid and non-hyperdiploid patients.Numerical gains of several recurring chromosomes were frequent among hyperdiploid patients while structural rearrangements of several chromosomes including 8q24.1 and 14q32 characterized non-hyperdiploid patients.With FISH,immunoglobulin heavy chain (IGH) gene rearrangements,especially fibroblast growth factor receptor 3 (FGFR3)/IGH and RB1 deletion/monosomy 13 were the most common abnormalities (43.4％).Amplification 1q21 was 10 times more frequent (42.5％) than del(1p36) and del(6q21).Conclusions We have successfully reported the comprehensive cytogenetic profiling of a cohort of newly-diagnosed myeloma patients in our population.This study indicates that the genetic and cytogenetic abnormalities,and their frequencies,in our study group are generally similar to other populations.