Deletion of 13q14.3 (del(13q)) is the most common cytogenetic abnormality in chronic lymphocytic leukemia (CLL) and implies a favorable prognosis. We explored the feasibility of detecting del(13q) by real-time quantitative polymerase chain reaction (PCR) for miR-15a and miR-16-1, whose loci are located in the deleted region. We analyzed 23 cases of B-CLL with monoallelic (10 cases) or biallelic del(13q) (5 cases) and used trisomy 12-positive CLL samples (n = 8) as control samples. As expected, miR-15a was expressed at significantly lower levels in monoallelic del(13qx1) samples compared with trisomy 12 control samples (P = .001). Biallelic del(13q) (del(13qx2)) samples showed further reduction of miR-15a levels compared with monoallelic del(13q) (del(13qx1)) (P = .009). In contrast, miR-16-1 expression levels were generally much lower and variable, with the highest levels detected in del(13qx1). Analyzed retrospectively, miR-15a levels differ among the del(13q) groups. However, only del(13qx2) miR-15a levels are reduced enough to determine the allelic status of an individual sample prospectively by real-time quantitative PCR.