We have applied boron neutron capture therapy (BNCT) to malignant brain tumors. Here we evaluated the survival benefit of BNCT for recurrent malignant glioma (MG). Since 2002, we have treated 22 cases of recurrent MG with BNCT. Survival time was analyzed with special reference to recursive partitioning analysis (RPA) classification, by Carson et al. Median survival times (MSTs) after BNCT for all patients and for glioblastoma as on-study histology at recurrence was 10.8 months (n=22; 95% CI, 7.3-12.8 months) and 9.6 months (n=19; 95% CI, 6.9-11.4 months), respectively. In our study, MST for the high-risk RPA classes was 9.1 months (n=11; 95% CI, 4.4-11.0 months). By contrast, the original journal data showed that the MST of the same RPA classes was 4.4 months (n=129; 95% CI, 3.6-5.4 months). BNCT showed a survival benefit for recurrent MG, especially in the high-risk group.