The purpose of this publication is to provide an account of the longhorned beetles of Colorado, to present new distributional records and to bring pertinent literature records together. One hundred ninety-three species and subspecies in 88 genera are listed, including thirty-eight new state records. The overall species distributions and host plants are included to provide an understanding of the zoogeography and possible origins of the species in the state. All available county records are included from the major institutional collections in Colorado, literature records, and numerous private collections. Previous literature citations for species not occurring or unlikely to occur in Colorado are discussed. Hyperplatys montana Casey is considered a valid species and removed from synonymy with H. aspersa (Say). Neoclytus ascendens LeConte is considered a synonym of N. leucozonus leucozonus (Castelnau & Gory).