The edible and common Gomphidius smithii
differs in that the cap is purplish grey and the lower part of the stem does not have yellow flesh, except sometimes at the extreme end. The edible but poor-tasting Gomphidius oregonensis
differs in that the cap is dingy-salmon in color and it grows in clusters where the stems are fused at the base.
See also Gomphidius glutinosus