Roots tuberous, tubers distally bulbous, 20-50 × 5-20 mm, parent and daughter tubers separated by connecting rhizome usually 10-15 mm. Stem erect, ca. 3-20 dm. Cauline leaves: blade 3-divided with more than 2 mm leaf tissue between deepest sinus and base of blade, 5-20cm wide, segment margins deeply cleft and toothed. Inflorescences racemes or panicles, terminal portion often contracted and capitate. Flowers blue, purple, or occasionally bluish white, 25-50 mm from tips of pendent sepals to top of hood; pendent sepals ca. 15 mm; hood conic-hemispheric, ca. 17 mm from receptacle to top of hood, ca. 20 mm wide from receptacle to beak apex.

Flowering summer (mid Jul-Sep). Meadows, thickets, and forests; 0-300 m; Alaska; Asia (Russian Far East and Japan).

Aconitum maximum subsp. maximum is a variable species. The only other species of Aconitum occurring with it on the Alaska Peninsula and the Aleutian Islands is A . delphiniifolium . Aconitum maximum subsp. maximum is reputedly extremely poisonous and was used as a source of arrow poison by the Aleuts (D. E. Moerman 1986; D. E. Brink 1982).