Cap: 6-20 cm; round to irregularly convex, becoming broadly convex or nearly flat; whitish, or with light brown colorations, especially towards the center; dry; bald, or with scattered fibrils; usually bruising yellow when rubbed, especially near the margin—the bruised areas then changing to brownish after some time has elapsed; the margin inrolled when young.
Gills: Free from the stem; white at first, then pinkish, and finally dark chocolate brown; close; when in the button stage, covered with a membranous white or yellowed partial veil that has patches of tissue on its underside.
Stem: 5-18 cm long; 1-3 cm thick; more or less equal; sometimes enlarged at the base; smooth; whitish, bruising yellow (then brownish); sometimes brownish in age; stuffed or hollowing; with a large, flaring, thick, yellow-staining ring on the upper portion.
Flesh: White and thick; yellowing when crushed; bright yellow in the base of the stem when sliced.
Odor and Taste: Odor unpleasant and phenolic, but sometimes faint; crush the flesh in the stem base to be sure.
Chemical Reactions: Cap surface yellow with KOH.
Spore Print: Dark chocolate brown.
Microscopic Features: Spores 4.5-6 × 3-4.5 µ; ellipsoid; smooth.