The compressibility at room temperature and pressure-temperature phase diagram of americium were measured to 35 kbar, and the electrical resistance at room temperature was measured to 120 kbar. Americium exhibits a higher compressibility than other actinides; in general, the physical properties of americium resemble rare earths more closely than the other actinides. The melting curve of americium obeyed the Kraut and Kennedy melting relation. Details of the phase diagram were in good agreement with recent work of Wade and Wolf. The melting point at 1 atm is 1173°C. There was an anomaly in the curve of resistance vs. pressure at 90 kbar; the effect may be due to a phase transition. © 1968.