OBJECTIVE The purpose of this study was to examine the effect of anxiety on cell-mediated immunity. METHODS The subjects consisted of 31 patients with anxiety disorders and 31 normal controls, who were gender-matched. Cell-mediated immune function was measured by the lymphocyte proliferative response to phytohemagglutinin (PHA), Interleukin-2 (IL-2) production, and natural killer cell activity (NKA). The extent of anxiety was assessed by the Hamilton rating scale for anxiety and the anxiety subscale of symptom checklist-90 revised (SCL-90-R). RESULTS The patients with anxiety disorders were significantly lower than the normal controls in lymphocyte proliferative response to PHA and IL-2 production. However, there was no significant difference in NKA between the two groups. Also, no significant correlation was found between the duration of illness or the degree of anxiety and each immune measure in patients with anxiety disorders. CONCLUSIONS The results suggest a reduced cell-mediated immune function in patients with anxiety disorders, compared with normal controls. These findings also imply that a variety of immune measures should be assessed at the same time in this kind of psychoneuroimmunology research. This would help elucidate the relationship between anxiety and immune function, which has been unclear in most previous research using a single immune measure.