Lupinus sellulus Kellogg (Papilionaeeae) is a polymorphic complex of the Sierra Nevada and Cascade mountains in California and Oregon considered to include five closely related varieties. Probable reticulate relationships among allied species are discussed. The taxonomic treatment includes keys, descriptions, distributional maps and illustrations of floral parts and leaflets. New combinations include L. sellulus var. lobbii (Gray ex Wats.) Cox, var. medius (Detl.) Cox and var. ursinus Eastw.) Cox. Taxonomic interpretations of Lupinus sellulus and its allies are diverse (Smith, 1927; Jepson, 1936; Detling, 1951; Phillips, 1955; Munz, 1959; Hitchcock et al., 1961). The present report is a segment of a biosystematic study (Cox, 1972a) of the herbaceous, perennial, caespitose lupines (Lupinus lepidus-L. caespitosus complex), primarily of the Sierra Nevada and Cascade mountain ranges with a few taxa found in the Great Basin ranging to the western Rocky Mountains. It is based on data derived from seed protein and alkaloid comparisons (.Cox, 1973), cytological evidence (Cox, 1972b), and detailed morphological, ecological and evolutionary comparisons made by laboratory and field studies conducted during five growing seasons. Grateful acknowledgment is made to curators of the following herbaria for loan of subject material: Atomic Energy Commission, BRY, CAS, DS, GH, IDS, ISC, JEPS, MO, NY, ORE, OSC, POM, RENO, RM, RSA, SMU, UC, UMO, US, UTC, V, WILLU, WS, WTU. (The symbols are those of Lanjouw and Stafleu, 1954.) Lupinus sellulus Kell. is distinguished by its basal rosette of leaves habit, generally fewer than three cauline leaves (rarely to six in var. medius), stems generally less than 3.5 dm tall, racemes slender, 4.5-11 cm long and 1.8-2.2 cm in diam, mostly exceeding the foliage, and flowers blue or violet with oblong-elliptic banners. It occurs throughout much of the central and northern Sierra Nevada Mountains of California and along the eastern face of the Cascade Mountains in Oregon (Fig. 1). The five variations treated here have been previously recognized as distinct entities, with varied taxonomic status applied. The morphological characters of each tends to blend with other entities, but, generally, each is distinct. The epithet, var. iobbii, is retained because these plants are recognizable by their small stature, small leaves and capitate to subcapitate racemes. Lupinus sellulus var. ursinus is a basalleaved, short pedunculate, densely pubescent group of plants of stature similar to var. lobbii but generally with longer and wider racemes with the flowers being more scattered. The variety medius has flowers somewhat smaller than var. sellulus but larger than var. artulus.