Thirty-four family group taxa and 57 characters are used to analyze cladistically the heteropteran infraorder Pentatomomorpha. Recognized are the 6 superfamilies Aradoidea, Coreoidea, Idiostoloidea, Lygaeoidea, Pentatomoidea, and Pyrrhocoroidea. New superfamily associations include the transfer of the Henicocorinae to Idiostoloidea, Piesmatoidea to Lygaeoidea, and the lygaeid subfamily Psamminae to Piesmatidae. The family Lygaeidae (sensu lato) is shown to be paraphyletic and is separated into 11 monophyletic family groups (Artheneidae, Blissidae, Cryptorhamphidae, Cymidae (sensu stricto), Geocoridae, Heterogastridae, Lygaeidae (sensu stricto), Ninidae, Oxycarenidae, Pachygronthidae, and Rhyparochromidae). Relationships are discussed, a revised classification is proposed, and keys to 6 superfamilies and 15 families included in Lygaeoidea are provided.