A new meroterpenoid named setosusin and two new tryptoquivalines were isolated as tremorgenic principles from an Ascomycete, Corynascus setosus, together with four known metabolited, fiscalin B, helvolic acid, helvolinic acid, and 2-(1-oxo-2-hydroxyethyl)furan. The structure of setosusin was determined from the chemical and spectral data and by X-ray crystallographic analysis of its deacetyl-dehydrated derivative. The two new tryptoquivalines were deduced to be 27-epi-isomers of tryptoquivaline and nortryptoquivaline from their spectral data supported by X-ray analysis.