The structure of simonyellin (5,9-dihydroxy-4-methoxy-7-methyl-1H,6H-naphtho[1,8-cd]pyran-1,6-dione), a naphthopyran from the lichen Simonyella variegata Steiner, has been established by X-ray structure analysis of a corresponding tetraacetate derivative. Crystals of simonyellin tetraacetate are triclinic, Pī, a 10.974(2), b 11.282(3), c 20.634(3)Ǻ, α 92.23(2)°, β 100.03(1)°, γ 117.80(2)°; Z 4. Refinement of 2754 data with I > 3σ(I) gave conventional R factors of 0.043 and 0.034.