The anatomy of the adult nervous system of the haematophagous bug Triatoma infestans has been studied by means of dissections and histology. The central nervous system comprises three nervous masses: the brain+suboesophageal ganglion, the prothoracic ganglion, and the posterior fused ganglion (meso+metathoracic+abdominal ganglia). The form of the brain is determined by the tubular head and the highly developed muscles of the pharyngeal pump. The prothoracic ganglion is located near the posternum, the posterior ganglionic mass near the mesosternum. A significative variation of the branching pattern of abdominal nerves is reported. The innervations of mouth parts, salivary glands, muscles, retrocerebral complex, spiracles, rectum, reproductive organs, alary muscles, and peripheral nerves are described.