Coronal rain are cool dense blobs that form in warm active region loops and fall along the guiding magnetic field to the solar surface. Antolin & Verwichte (2011) presented a first observational study with Hinode/SOT in In Ca II H in which multiple coronal rain blobs are seen to oscillate transversely in phase. I will discuss observations and theory of magnetohydrodynamic oscillations in coronal rain and what they can reveal about the dynamics of coronal rain and the structure of the magnetic loop supporting it.