A new amino acid (I) was isolated from a toxic mushroom, Russula subnigricans HONGO, and characterized as (2S,3R)-( - )-3-hydroxybaikiain [(2S,3R)-( - )-1,2,3,6-tetrahydro-3-hydroxypyridine-2-carboxylic acid]. (S)-(-)-Baikiain (II), (S)-(-)-pipecolic acid (III), ergosterol (IV), ergosteryl peroxide (V) and cerevisterol (VI) were also isolated and identified.