The decline of dopamine and norepinephrine after intravenous alpha-methyltyrosine was used to determine the rate constants for catecholamine turnover in the rat prefrontal cortex, olfactory tubercle and striatum. Dopamine turnover varied more between brain regions and was generally faster than the corresponding norepinephrine turnover. Prefrontal cortical dopamine was unaffected by dorsal noradrenergic bundle lesions. The turnover of prefrontal cortical dopamine was found to be 2-4 times faster than dopamine turnover in the olfactory tubercle and striatum.