Postherpetic neuralgia (PHN) is a severe sequela of herpes zoster (HZ). Until now, only age and pain severity were considered predisposing factors for the development of PHN. We evaluated 49 patients with acute phase HZ, 10 of whom developed PHN (Group A) and 39 of whom did not develop PHN (Group B). Twenty-five healthy volunteers similar in age and gender distribution to the study group were recruited as controls (Group C). Numbers of serum CD3(+) (pan-T lymphocytes), CD4(+) (helper/inducer), and CD8(+) (suppressor/cytotoxic) lymphocytes were decreased significantly in Groups A and B relative to the control group, but there were no statistical differences between Groups A and B. Interleukin (IL)-1beta, IL-6, tumor necrosis factor (TNF)-alpha, IL-8, and IL-10 were significantly elevated in Groups A and B relative to Group C. IL-6 was significantly higher in Group A than in Group B, and was significantly positively correlated with pain severity scored on a visual analog scale. Therefore, we suggest that the inflammatory response, especially that of IL-6, in the acute phase of HZ may be associated with hyperalgesia and the development of PHN.