Abstract: Investigating clonal origin, assessment of severity of disease of multiple myeloma (MM) METHOD:Using Clonal immunogobulin heavy chain (IgH) gene rearrangement as a gene marker of myeloma 42 bone merrow specimens from MM. Patients were detected the ceonal IgH rearrengement by polymease chaim reaction (PCR). 34 of 42 marrow specimens showed clonal IgH gene rearrangement which was 80.95% positive percentage. However, the positine shpeimens did not correlate with the clinical stage and immune classification (P＞0.05 ). There was no clonal IgH gene rearrangement detected in 10 patients with reactive plasmacytosis (RP) and 12 normal sntjects. 16(66.67%) of the 24 peripheral blood specimens was detected clonal IgH gene rearrangement. The incidence of clonal IgH gene rearrangement in peripheral blood of MM patients with stage Ⅱ and Ⅲ was much higher than that with stage Ⅰ (P＜0.025), but did not correlete with immune classification (P＞0. 05). The clonal IgH gene rearrangement detected in peripheral blood was identical with that in bone marrow within the same patient,but there was difference among patients. Thus detection of clonal IgH gene rearrangement in MM may provide important information for study of clonal origin ofmyeloma and assessment of severity of disease.