Separation of the ethyl acetate extract of marine fungus Cryptosphaeria eunomia var. eunomia afforded a new pimarane-type diterpene 1 together with known compounds, 2, 4, and 5, whose absolute configurations were unknown. During recrystallization experiments using chloroform, compounds 1, 2, and 5 gave crystals suitable for X-ray analyses, which revealed that the crystals incorporated chloroform molecules in the crystal lattices. Based on the intense anomalous scattering by chlorine, the absolute configurations of 1, 2, and 5 were unambiguously determined.