Two new 5-substituted dihydrofuranones, named sapinofuranones A and B (1 and 2), were isolated from liquid cultures of Sphaeropsis sapinea, a phytopathogenic fungus causing a wide range of disease symptoms on conifers. A fungal strain isolated from Cupressus macrocarpa produced both 1 and 2 at concentrations higher than those produced by the strain isolated from Cupressus sempervirens. Bioassay of 1 and 2 gave epinasty and brown discoloration on petioles of tomato leaves, sapwood stain on inner cortical tissues of the stem of cypress seedlings, and yellowing and needle blight on pine seedlings. Compounds 1 and 2 were characterized, using spectroscopic and chemical methods, as two new 4-[(2Z, 4E)-1-hydroxy-2,4-hexadienyl]butan-4-olides, which are epimers at C-1 of the side chain. The absolute stereochemistry of this chiral center, determined by application of the Mosher's method, proved to be S and R in 1 and 2, respectively.