Spontaneous eye blink rates, psychiatric symptoms and response to neuroleptic medication may all be mediated by dopamine. Fixed doses of haloperidol, a dopamine blocking agent, were administered for six weeks to 17 chronic schizophrenic patients who had been previously withdrawn from all medications. The change in blink rates caused by haloperidol corresponded to a change in the thought disturbance syndrome which measures positive symptoms (r = .48, P less than .05). The relationship was particularly clear in patients with normal cerebral ventricles (r = .74, P less than .01).