Artemisia annua L.(Compositae) is a traditional Chinese herbal medicine for treatment of fever and malaria. Artemisinin, an antimalarial principle, arteannuin B, and artemisinic acid, a biogenetic and semisynthetic precursor of artemisinin, were isolated from the plant. During the course of the isolation of artemisinic acid, we frequently observed a fibrous crystal which has a very different solubility pattern from artemisinic acid in organic solvents. Its ¹H-NMR spectra was almost: identical with that of artemisinic acid except upfield shifted olefinic signals. MS, IR, and UV spectra showed the same results as those of artemisinic acid. Through the two-dimensional NMR experiments, full ¹H- and ^(13)C- NMR assignments of the material were made and consequently characterized as 7-epi-artemisinic acid.