Depression is a prevalent and impairing psychiatric disorder that affects how we feel and how we think about ourselves and the world around us. Cognitive theories of depression have long posited that various thought processes are involved in the development, maintenance, and recurrence of depressive episodes. Contemporary research has utilized experimental procedures to examine cognitive processes in depressed individuals as well as the nature of the relation of these processes to the emotion dysregulation that is central to the disorder. For example, investigators have assessed the ways in which depression alters aspects of information processing, including attention and perception, interpretation, and memory processes; this research has generated relatively consistent findings. In addition, researchers have attempted to identify and elucidate the cognitive mechanisms that may link these biases in information processing to emotion dysregulation in depression. These mechanisms include inhibitory processes and deficits in working memory, ruminative responses to negative mood states, and the inability to use positive and rewarding stimuli to regulate negative mood. Results of these investigations converge on the formulation that depression is associated with increased elaboration of negative information, difficulties in cognitive control when processing this information, and difficulties disengaging from this information. Research examining cognitive aspects of depression not only enhances our understanding of this common and costly disorder, but also has implications for the treatment of depression and for future investigations of the biological foundations of this disorder.