Chromosome 13q14 deletion is one of the most common cytogenetic abnormalities in multiple myeloma (MM). LSI (locus-specific identification)-RB1 (13q14.1-14.2 region) and LSI-D13S319 (13q14.3 region) probes are usually used to detect 13q14 deletion. The aims of this study was to compare the incidence of chromosome 13q14.1-14.2 and 13q14.3 deletion and to detect 13q14 deletion size and number of involved cells in MM patients. The chromosome 13q14 region was detected by fluorescence in situ hybridization using probes LSI-RB1 and LSI-D13S319 in plasma cells of 112 MM patients. The results showed that 47.3% (53 out of 112) MM patients had both LSI-RB1 and LSI-D13S319 13q14 deletion (cut-off value: 7%), and the deletion rates detected by probes LSI-RB1 and LSI-D13S319 were accordant. The positive rates of 13q14 deletion were 46.4% and 47.3% respectively when the cut-off level was increased to 20%, and the corresponding rate was 98%. MM patients carrying 13q14 deletion showed 18% - 98% (median value: 72.5%) and 22% - 98.5% (median value: 76.5%) of deleted nuclei involving the RB1 and the D13S319 locus (P = 0.38). There were 67.9% (36 out of 53) and 66% (35 out of 53) cases carrying > 65% of 13q14.1-14.2 and 13q14.3 deleted nuclei as high proportion deletion patients, respectively (P = 0.188). The positive rate of the high proportion deletion patients had still no difference between LSI-RB1 and LSI-D13S319 groups when the cut-off value was defined as 85% (P = 0.439). In conclusion, in this cohort of 112 MM patients, there was no significant difference between the LSI-RB1and LSI-D13S319 probes to detect 13q14 deletion. Both LSI-RB1 and LSI-D13S319 probes can be selected to detect 13q14 deletion in MM patients. All the 53 MM patients with 13q14 deletion had deletions of 13q14.1-14.2 and 13q14.3 regions, which is a large deletion as one of the important characters in MM patients with 13q14 deletion.