There is considerable empirical support for the use of cognitive therapy in the treatment of mild to moderately severe acute major depression. More recent research has focused on the utility of this approach in severe or chronic depressive disorders, in relapse prevention and also on the potential benefits of combining cognitive therapy with medication. This paper attempts to clarify the empirical data on these important issues in order to identify further the role of cognitive therapy in day-to-day clinical practice. It also provides an overview of findings regarding predictors of response to cognitive therapy and the possible mediators of its effects.