The structures of two new acetylenic compounds from Mycena viridimarginata were elucidated by spectroscopic methods and some chemical transformations. The major metabolite was lO-hydroxyundeca-2,4,6,8 tetraynamide and the minor one was 3,4,13-trihydroxytetradecaca-5,7,9,11-tetraynoic acid y-lactone. Another compound, methyl-3,4,13-trihydroxytetradeca-5,7,9,11-tetraynoate, was found to be an artifact from the y-lactone produced on the Sephadex LH-20 column. Furthermore, model compounds were prepared to establish the chromophoric system of the major metabolite.