OBJECTIVE To determine the incidence and clinical significance of chromosome 13q14 deletion in multiple myeloma (MM). METHODS Bone marrow samples were collected from 132 newly diagnosed MM patients referred to our hospital. Interphase fluorescence in situ hybridization (i-FISH) combined with magnetic activated cell sorting (MACS) were performed on chromosome 13q14 (RB-1). RESULTS (1) i-FISH was used to investigate CD138-enriched bone marrow MM cells and revealed a 13q14 deletion rate of 51.5% (68/132), while conventional cytogenetic (CC) analysis revealed 13q deletions/monosomy 13 (Δ13) only of 5.0%(6/120). (2) Univariate analysis showed that 13q14 deletion rate by i-FISH > 25%, bone marrow plasma cells > 50%, ISS stage and β(2)-MG ≥ 5.5 mg/L were associated with shorter overall survival (OS). Multivariate analysis revealed that 13q14 deletion rate by i-FISH > 25% was an independent unfavorable factor (P = 0.042). (3) Patients treated with bortezomib had a much better response than those treated with traditional chemotherapy (P = 0.001). There was no significant difference in OS between patients received bortezomib with and without 13q14 deletion (P > 0.05), indicating that bortezomib could reverse the poor prognosis of 13q14 deletion. CONCLUSIONS (1) i-FISH followed CD138 cell sorting appears to be a highly sensitive method for detecting 13q14 deletion. (2) 13q14 deletion rate by i-FISH > 25% is an independent unfavorable factor. (3) Bortezomib could reverse the poor prognosis of 13q14 deletion.