The study of transformations of materials under high pressures promises to yield modifications with important applications in materials science and other fields including, by way of example, the dense metallic modification of hydrogen possessing extremely high superconducting properties. This work presents recent theoretical and experimental information gathered on phase diagrams of 96 elements. Data is presented on first- and second-phase transitions, melting lines, crystal structures of the stable and metastable phases, important phase properties such as the Curie and Neel temperature, and the superconducting temperature. Information is provided on elements' liquid state, amorphization, and metallization. Temperature-pressure diagrams are given for most of the elements.