Three single nucleotide polymorphisms (SNPs) in SCN9A and two in SCN10A were investigated using whole-genome genotyping data from 186 Japanese breast or ovarian cancer patients classified into two groups as follows: cases that developed taxane-induced grade 2–3 neuropathy (N = 108) and controls (N = 78) with grade 0–1 neuropathy. The gene discussed is SCN9A; the disease is neuropathy.