We present a comparison between the experimental and theoretical LEED rotation diagrams obtained from the (001) surface of Al. The experiment was performed at E=20 eV over a large range of polar angles with the help of a new LEED goniometer which permits us to vary the polar angle between 0° and 90° and the azimuthal angle between 0° and 360° without opening the system. Realizing that rotation diagrams (which exhibit most directly dynamical effects) constitute perhaps the most crucial test of any dynamical theory of LEED, we have performed calculations using the following formalisms: multiple scattering theory of McRae–Kambe, band structure-matching, one-dimensional multiple scattering model, and inelastic collision model. The results of these calculations (performed for the same incidence conditions) are compared and their relationship with experiment is discussed.