Patient-derived risks are defined by haplotypes. A patient’s haplotypes can be used to assess risks associated with rs915654 (transplant-related mortality), rs2075800 (grades III-IV acute GVHD), and rs429916 (survival, disease-free survival, and transplant-related mortality). The number of favorable genotypes among these three positions depends on the combination of the patient’s maternal and paternal haplotypes. Illustrated are patients whose haplotypes contribute 3, 2, 1, or 0 favorable genotypes at the 3 SNP positions. The patient with ab haplotypes has the TA-GA-CC haplotype at SNPs rs915654, rs2075800, and rs429916, respectively; these genotypes are all favorable (Table 2). The patient with bc haplotypes has 2 favorable (rs2075800AA and rs429916CC) and 1 unfavorable (rs915654AA) genotypes. The patient with de haplotypes has 1 favorable (rs429916CC) and 2 unfavorable (rs915654TT and rs2075800GG) genotypes. The patient with fg haplotypes has all unfavorable genotypes. The total number of favorable SNPs is defined as the combination of the maternal and paternal haplotypes. For example, the presence of HLA-A3-B7-DR15 (a haplotype) with HLA-A2-B44-DR4 (b haplotype) yields 3 favorable (rs915654, rs2075800, and rs429916) genotypes, but the same HLA-A2-B44-DR4 (b haplotype) with HLA-A3-B7-DR11 (c haplotype) yields 2 favorable genotypes. Two individuals with the same HLA tissue type may have different numbers of favorable SNPs because of haplotype diversity. For example, an individual with the HLA-A1,29-B8,44-DR3,7 tissue type can encode either TT-GG-CC (1 favorable SNP; haplotypes de) or TT-GG-AA (0 favorable SNPs; haplotypes fg) as a result of haplotypic diversity (Table 3; supplemental Table 2). Although a patient’s haplotypes cannot be modified, knowledge of the haplotypes can be used for risk assessment, and risks can be lowered through the avoidance of donors with unfavorable genotypes or SNP mismatching.