The demonstration that behavioral states and CNS processes are associated with immune function suggests that there may be a relationship between anxiety and the immune system. Stress and immunity have been studied extensively, but there have been relatively few studies of anxiety and immunity. Many of the neurobiologic processes associated with stress and with depression have been observed in anxiety and are known to influence the immune system. A review of the immune response to stress and of immune alterations in depression has been presented in an effort to provide further understanding of the biology of anxiety. It appears that a variety of factors such as age; sex; nature, intensity, and chronicity of a stressful life events; and psychologic response to life stress need to be considered in the investigation of behavior and immunity. The biologic effects of stress on immunity are multifaceted, including complex neuroendocrine and neurotransmitter interactions. Further investigation is required of anxiety and immunity in clearly delineated and diagnosed anxiety states and disorders. Such studies may help to elucidate the pathophysiology of anxiety disorders.