Fourteen patients with documented Huntington's chorea had circulating growth hormone levels measured during an oral glucose tolerance test before and after a three day period of l-dopa administration. In the baseline test there was failure of suppression of hGH release after oral glucose, and/or a late rise to abnormally high levels. After l-dopa priming, mean fasting growth hormone levels rose considerably in these patients (from 3.6 ± 0.6 ng/ml to 17.9 ± 2.3 ng/ml), but showed a lesser rise in control subjects (from 2.5 ± 0.4 ng/ml to 6.4 ± 1.3 ng/ml). Although there was a sharp rise of growth hormone after oral glucose plus l-dopa ir control subjects, the patients with Huntington's chorea had a paradoxical and complete suppression of their elevated fasting growth hormone levels under these conditions. Although these observations may not be specific for Huntington's chorea, they may be explained by pathologic involvement of the hypothalamus or by a possible increased sensitivity to intracerebrai dopamine in patients with this disease.