Postherpetic neuralgia is frequently painful, incapacitating, mood depressing, and sometimes lifelong. We investigated the influence of duration from eruption to nerve blocks in conjunction with patients age on analgesic and preventive effect for postherpetic neuralgia. We retrospectively evaluated 50 outpatient medical records for the above T4 dermatome. Patients had been referred to pain clinic and were treated over 2weeks from Jan. 1988 to Dec. 1993. Fifty patients were divided into 4 groups as follows: Group I (a): less than 4weeks from eruption to nerve block and younger than 65 years old. Group I (b): less than 4weeks from eruption to nerve block and older than 65 years old. Group II (a): more than 4weeks from eruption to nerve block and younger than 65 years old. Group II(b): more than 4weeks from eruption to nerve block and older than 65 years old. Mean number of stellate ganglion blocks were 29.7. Tramadol, amitriptyline, nicardipine were most commonly prescribed. Group I (a): had the most improvement rate(77.8%) as compared with other group(46.6, 52.7, 56.0%). Number of patients who complained of severe pain (VAS > 5) were 0, 3(39%), 2(15.4%), 5(30%) in I (a), I (b), II (a), II (b) group respectively. In conclusion, analgesic effect was best in cases of patients younger than 65 years old whose treatment were started within 4 weeks of eruption. Patients older than 65 yrs, analgesic effect did not vary on the timing of treatment.