This article provides a review of empirical evidence linking emotional processes to immune function in humans. Acute stressors have produced mixed effects on immunity, presumably through differential activation of physiological stress systems. Chronic stress has been associated with suppression of immune function, and there is evidence that the immune system may not adapt over time. Effects of stress accompanying social disruption and psychological depression, when demonstrated, have been consistently adverse. Certain personality styles may enhance or degrade immune response. Relationships between psychosocial factors and immunity have been identified for several diseases, including cancer, acquired immune deficiency syndrome, and autoimmune diseases; psychosocial interventions have been tested with variable results. Theoretical and methodological considerations are summarized and directions for future research suggested.