Experiments on solid iodine under pressure are reviewed. Theoretical results obtained on solid iodine by the full-potential linear muffin-tin orbital method are reviewed. The pressure dependences of the Raman-active modes of molecular solid bromine have been studied theoretically by the same method. The calculated results reproduce recent experimental results very well. After metallization, the softening of frequencies that is seen is not the same as in experiments. This contrasts with the case for solid iodine.