T he voltage-gated sodium-channel type IX α subunit, known as Na_v1.7 and encoded by the gene SCN9A, is located in peripheral neurons and plays an important role in action potential production in these cells. Recent genetic studies have identified Na_v1.7 dysfunction in three different human pain disorders. Gain-of-function missense mutations in Na_v1.7 have been shown to cause primary erythermalgia and paroxysmal extreme pain disorder, while nonsense mutations in Na_v1.7 result in loss of Na_v1.7 function and a condition known as channelopathy-associated insensitivity to pain, a rare disorder in which affected individuals are unable to feel physical pain. This review highlights these recent developments and discusses the critical role of Na_v1.7 in pain sensation in humans.