Disclosed is a continuous process for the preparation of ingenol-3-mebutate by reaction, in solution, of ingenol or ingenol anion and angelic anhydride or an equivalent angelylating agent. The continuous flow process is preferably performed in the presence of a base such as lithium hexamethyl disilazane (LiHMDS) and/or an activating agent such as dicyclohexylcarbodiimide (DCC). Also disclosed is a process for recycling the other reaction products obtained in the continuous process for preparation of ingenol-3-mebutate for formation of ingenol, which can then be recycled to form ingenol-3-mebutate.