Various drugs that alter central monoamine activity were given to monkeys to determine effects on blink rate. Chronic pargyline treatment raised the mean +/- SD blink rate slightly to 18.2 +/- 5.3 blinks/90 sec. When phenylethylamine was added to chronic pargyline treatment, blinks increased from a base line of 16.8 +/- 7.6 blinks/90 sec to 37 +/- 15 blinks/90 sec. Apomorphine (0.36 mg/kg) raised blinks from a base lone of 12.2 +/- 2.8 blinks/90 sec. to 41.9 +/- 10.3 blinks/90 sec. and reversed a decrease in blinking caused by haloperidol. The neurochemical basis of blinking and implications for tardive dyskinesia are discussed.