  Recent developments on the rotational instabilities of relativistic stars are
reviewed. The article provides an account of the theory of stellar
instabilities with emphasis on the rotational ones. Special attention is being
paid to the study of these instabilities in the general relativistic regime.
Issues such as the existence relativistic r-modes, the existence of a
continuous spectrum and the CFS instability of the w-modes are discussed in the
second half of the article.
