Epiartemisinin (7) was prepared by the base epimerization of artemisinin (1) and its structure determined by X‐ray analysis. The antimalarial activity of 7 against the chloroquine‐sensitive and resistant strains of Plasmodium berghei and P. yoelii in the mouse was compared with that of the highly effective schizonticide 1 and found to be drastically diminished. It is argued that the mode of action on the intraerythrocytic parasite by 7 is compromised by steric hindrance arising from the α‐disposed Me group. In the initial step, intimate complexation with heme is hindered or biased to favor the formation of a less potent C‐centered radical, the final lethal agent.