The first part of a series of notes and new taxa supplementary to the author's The Genus Echinocereus (1985) is presented. The following new names, based on the results of studies in the field and of documented plants in cultivation, are published: Echinocereus cinerascens var. septentrionalis (var. nov.), E. cinerascens var. tulensis (stat. nov.), E. stramineus var. occidentalis (var. nov.), E. parkeri (sp. nov.), E. parkeri var. gonzalezii (var. nov.), E. rayonesensis (sp. nov ), E. longisetus var. delaetii (stat. nov.) and E. polyacanthus var. huitcholensis (stat. nov.). In addition, the circumscription of E. viereckii var. morricalii is substantially expanded, E. freudenbergeri is reinstated as a species, and E. knippelianus is tentatively referred to Sect. Echinocereus, E. viridiflorus Group. The grouping of species in Sect. Echinocereus is revised, and the descriptions of various species in Sections 1–4 amplified.