The present invention relates to a novel crystalline form of ingenol mebutate, methods of preparation thereof, and to its use. More specifically, the invention relates to the conversion of amorphous ingenol mebutate (ingenol-3-angelate, PEP005) to a crystalline form, which was characterized by single crystal X-Ray crystallography (XRC), attenuated total reflectance Fourier transform infrared (FTIR-ATR) spectroscopy and Differential Scanning calorimetry (DSC).