Two trials of chlorprothixene were carried out, mainly on patients with moderate to severe post-herpetic neuralgia. When the drug was given as 50 mg b.d. to outpatients, unpleasant side-effects were more important than slight effects in alleviating pain. When the drug was given as 50 mg 6 hourly to inpatients for 5 days only, there was alleviation of constant chronic pain in a third of the patients; the effect is still lasting over a period of months in a few patients. The side-effects during the course of treatment are prominent. It is concluded that the drug is worth trying in the course recommended by Farber and Burks [1] when other means of controlling postherpetic neuralgia have failed. It would be best to give the course only to inpatients.