The objective of this study was to investigate expression of interferon regulatory factors (ICSBP/IRF8) and the potential role of DNA methylation in silencing ICSBP/IRF8 gene in multiple myeloma (MM) cell line U266 and bone marrow mononuclear cells from 10 MM patients (MM-BMMNC). The bone marrow mononuclear cells from 10 healthy persons (N-BMMNC) were collected and used as normal controls. Expression of ICSBP/IRF8 gene was detected by real-time fluorescence quantitative PCR (using 2(-ΔΔCT) to calculate); DNA methylation level of the ICSBP/IRF8 gene was measured using methylation-specific PCR (using the ratio of interest gene ICSBP/IRF8 and internal reference β-actin expression as results). The results showed that as compared with N-BMMNC the lower expression of ICSBP/IRF8 gene was found in U266 cells and MM-BMMNC, the hypermethylation of the CpG island in the ICSBP/IRF8 promoter was observed, there were significant differences between N-BMMNC and MM-BMMNC or U266 cells (P < 0.05). It is concluded that the expression of ICSBP/IRF8 gene can be silenced in the MM-BMMNC and U226 cells. As the hypermethylation of CpG island in ICSBP/IRF8 promoter is a frequent event in MM cells, the ICSBP/IRF8 gene silencing caused by DNA methylation may take part in the pathogenesis and development of MM.