Abstract Simulations suggest that the strong phase object approximation of dynamical scattering may allow extracting crystallographic phase information from single 2D electron diffraction patterns of 3D protein crystals using probabilitistic procedures. Unlike other phasing methods, the procedure does not requires any additional knowledge – like real space images, atomicity, non-crystallographic symmetry, the presence or location of disordered solvent or the availability of a support with a known structure. In specific cases, the availability of precession electron diffraction data can further improve the phases.