6-Hydroxy-dopamine was administered into the third ventricle of adult male rats. After 2 successive 250 mug doses of 6-OH-dopamine, the levels of norepinephrine and dopamine in the median eminence and arcuate nucleus fell to 15-20% of the control value. The amount of luteinizing hormone releasing hormone (LH-RH) in these same hypothalamic areas, however, was unchanged. It is concluded that LH-RH containing cells are distinct from catecholaminergic neurons.